Method and circuit for down-converting a signal

ABSTRACT

Methods, systems, and apparatuses for down-converting an electromagnetic (EM) signal by aliasing the EM signal are described herein. Briefly stated, such methods, systems, and apparatuses operate by receiving an EM signal and an aliasing signal having an aliasing rate. The EM signal is aliased according to the aliasing signal to down-convert the EM signal. The term aliasing, as used herein, refers to both down-converting an EM signal by under-sampling the EM signal at an aliasing rate, and down-converting an EM signal by transferring energy from the EM signal at the aliasing rate. In an embodiment, the EM signal is down-converted to an intermediate frequency (IF) signal. In another embodiment, the EM signal is down-converted to a demodulated baseband information signal. In another embodiment, the EM signal is a frequency modulated (FM) signal, which is down-converted to a non-FM signal, such as a phase modulated (PM) signal or an amplitude modulated (AM) signal.

CROSS-REFERENCE TO OTHER APPLICATIONS

This is a continuation of U.S. application “Method And Circuit ForDown-Converting A Signal,” Ser. No. 10/394,069, filed Mar. 24, 2003,which is a continuation of U.S. application “Method and System forDown-Converting a Signal Using a Complimentary FET Structure forImproved Dynamic Range,” Ser. No. 09/293,342, filed Apr. 16, 1999(U.S.Pat. No. 6,687,493), which is a continuation-in-part application of U.S.application “Method and System for Down-Converting ElectromagneticSignals,” Ser. No. 09/176,022, filed Oct. 21, 1998, (U.S. Pat. No.6,061,551), each of which is incorporated herein by reference in itsentirety.

The following applications of common assignee are related to the presentapplication, and are herein incorporated by reference in theirentireties:

“Method and System for Frequency Up-Conversion,” Ser. No. 09/176,154,filed Oct. 21, 1998, (U.S. Pat. No. 6,091,940).

“Method and System for Ensuring Reception of a Communications Signal,”Ser. No. 09/176,415, filed Oct. 21, 1998, (U.S. Pat. No. 6,061,555).

U.S. application “Integrated Frequency Translation and Selectivity,”Ser. No. 09/175,966, filed Oct. 21, 1998, (U.S. Pat. No. 6,049,706).

“Universal Frequency Translation, and Applications of Same,” Ser. No.09/176,027, filed Oct. 21, 1998, (Abandoned).

“Method and System for Down-Converting Electromagnetic Signals HavingOptimized Switch Structures,” Ser. No. 09/293,095, filed Apr. 16, 1999,(U.S. Pat. No. 6,580,902).

“Method and System for Frequency Up-Conversion Having Optimized SwitchStructures,” Ser. No. 09/293,097, filed Apr. 16, 1999, (Abandoned).

“Method and System for Frequency Up-Conversion With a Variety ofTransmitter Configurations,” Ser. No. 09/293,580, filed Apr. 16, 1999,(U.S. Pat. No. 6,542,722).

“Integrated Frequency Translation And Selectivity With a Variety ofFilter Embodiments,” Ser. No. 09/293,283, filed Apr. 16, 1999, (U.S.Pat. No. 6,560,301).

“Frequency Translator Having a Controlled Aperture Sub-Harmonic MatchedFilter,” Ser. No. 60/129,839, filed Apr. 16, 1999.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to down-conversion of electromagnetic (EM)signals. More particularly, the present invention relates todown-conversion of EM signals to intermediate frequency signals, todirect down-conversion of EM modulated carrier signals to demodulatedbaseband signals, and to conversion of FM signals to non-FM signals. Thepresent invention also relates to under-sampling and to transferringenergy at aliasing rates.

2. Related Art

Electromagnetic (EM) information signals (baseband signals) include, butare not limited to, video baseband signals, voice baseband signals,computer baseband signals, etc. Baseband signals include analog basebandsignals and digital baseband signals.

It is often beneficial to propagate EM signals at higher frequencies.This is generally true regardless of whether the propagation medium iswire, optic fiber, space, air, liquid, etc. To enhance efficiency andpracticality, such as improved ability to radiate and added ability formultiple channels of baseband signals, up-conversion to a higherfrequency is utilized. Conventional up-conversion processes modulatehigher frequency carrier signals with baseband signals. Modulationrefers to a variety of techniques for impressing information from thebaseband signals onto the higher frequency carrier signals. Theresultant signals are referred to herein as modulated carrier signals.For example, the amplitude of an AM carrier signal varies in relation tochanges in the baseband signal, the frequency of an FM carrier signalvaries in relation to changes in the baseband signal, and the phase of aPM carrier signal varies in relation to changes in the baseband signal.

In order to process the information that was in the baseband signal, theinformation must be extracted, or demodulated, from the modulatedcarrier signal. However, because conventional signal processingtechnology is limited in operational speed, conventional signalprocessing technology cannot easily demodulate a baseband signal fromhigher frequency modulated carrier signal directly. Instead, higherfrequency modulated carrier signals must be down-converted to anintermediate frequency (IF), from where a conventional demodulator candemodulate the baseband signal.

Conventional down-converters include electrical components whoseproperties are frequency dependent. As a result, conventionaldown-converters are designed around specific frequencies or frequencyranges and do not work well outside their designed frequency range.

Conventional down-converters generate unwanted image signals and thusmust include filters for filtering the unwanted image signals. However,such filters reduce the power level of the modulated carrier signals. Asa result, conventional down-converters include power amplifiers, whichrequire external energy sources.

When a received modulated carrier signal is relatively weak, as in, forexample, a radio receiver, conventional down-converters includeadditional power amplifiers, which require additional external energy.

What is needed includes, without limitation:

an improved method and system for down-converting EM signals;

a method and system for directly down-converting modulated carriersignals to demodulated baseband signals;

a method and system for transferring energy and for augmenting suchenergy transfer when down-converting EM signals;

a controlled impedance method and system for down-converting an EMsignal;

a controlled aperture under-sampling method and system fordown-converting an EM signal;

a method and system for down-converting EM signals using a universaldown-converter design that can be easily configured for differentfrequencies;

a method and system for down-converting EM signals using a localoscillator frequency that is substantially lower than the carrierfrequency;

a method and system for down-converting EM signals using only one localoscillator;

a method and system for down-converting EM signals that uses fewerfilters than conventional down-converters;

a method and system for down-converting EM signals using less power thanconventional down-converters;

a method and system for down-converting EM signals that uses less spacethan conventional down-converters;

a method and system for down-converting EM signals that uses fewercomponents than conventional down-converters;

a method and system for down-converting EM signals that can beimplemented on an integrated circuit (IC); and

a method and system for down-converting EM signals that can also be usedas a method and system for up-converting a baseband signal.

SUMMARY OF THE INVENTION

Briefly stated, the present invention is directed to methods, systems,and apparatuses for down-converting an electromagnetic (EM) signal byaliasing the EM signal, and applications thereof. Generally, theinvention operates by receiving an EM signal. The invention alsoreceives an aliasing signal having an aliasing rate. The inventionaliases the EM signal according to the aliasing signal to down-convertthe EM signal. The term aliasing, as used herein and as covered by theinvention, refers to both down-converting an EM signal by under-samplingthe EM signal at an aliasing rate, and down-converting an EM signal bytransferring energy from the EM signal at the aliasing rate.

In an embodiment, the invention down-converts the EM signal to anintermediate frequency (IF) signal.

In another embodiment, the invention down-converts the EM signal to ademodulated baseband information signal.

In another embodiment, the EM signal is a frequency modulated (FM)signal, which is down-converted to a non-FM signal, such as a phasemodulated (PM) signal or an amplitude modulated (AM) signal.

The invention is applicable to any type of EM signal, including but notlimited to, modulated carrier signals (the invention is applicable toany modulation scheme or combination thereof) and unmodulated carriersignals.

Further features and advantages of the invention, as well as thestructure and operation of various embodiments of the invention, aredescribed in detail below with reference to the accompanying drawings.It is noted that the invention is not limited to the specificembodiments described herein. Such embodiments are presented herein forillustrative purposes only. Additional embodiments will be apparent topersons skilled in the relevant art(s) based on the teachings containedherein.

The drawing in which an element first appears is typically indicated bythe leftmost digit(s) in the corresponding reference number.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be described with reference to theaccompanying drawings wherein:

FIG. 1 illustrates a structural block diagram of an example modulator;

FIG. 2 illustrates an example analog modulating baseband signal;

FIG. 3 illustrates an example digital modulating baseband signal;

FIG. 4 illustrates an example carrier signal;

FIGS. 5A–5C illustrate example signal diagrams related to amplitudemodulation;

FIGS. 6A–6C illustrate example signal diagrams related to amplitudeshift keying modulation;

FIGS. 7A–7C illustrate example signal diagrams related to frequencymodulation;

FIGS. 8A–8C illustrate example signal diagrams related to frequencyshift keying modulation;

FIGS. 9A–9C illustrate example signal diagrams related to phasemodulation;

FIGS. 10A–10C illustrate example signal diagrams related to phase shiftkeying modulation;

FIG. 11 illustrates a structural block diagram of a conventionalreceiver;

FIG. 12A–D illustrate various flowcharts for down-converting anEM-signal according to embodiments of the invention;

FIG. 13 illustrates a structural block diagram of an aliasing systemaccording to an embodiment of the invention;

FIGS. 14A–D illustrate various flowcharts for down-converting an EMsignal by under-sampling the EM signal according to embodiments of theinvention;

FIGS. 15A–E illustrate example signal diagrams associated withflowcharts in FIGS. 14A–D according to embodiments of the invention;

FIG. 16 illustrates a structural block diagram of an under-samplingsystem according to an embodiment of the invention;

FIG. 17 illustrates a flowchart of an example process for determining analiasing rate according to an embodiment of the invention;

FIGS. 18A–E illustrate example signal diagrams associated withdown-converting a digital AM signal to an intermediate frequency signalby under-sampling according to embodiments of the invention;

FIGS. 19A–E illustrate example signal diagrams associated withdown-converting an analog AM signal to an intermediate frequency signalby under-sampling according to embodiments of the invention;

FIGS. 20A–E illustrate example signal diagrams associated withdown-converting an analog FM signal to an intermediate frequency signalby under-sampling according to embodiments of the invention;

FIGS. 21A–E illustrate example signal diagrams associated withdown-converting a digital FM signal to an intermediate frequency signalby under-sampling according to embodiments of the invention;

FIGS. 22A–E illustrate example signal diagrams associated withdown-converting a digital PM signal to an intermediate frequency signalby under-sampling according to embodiments of the invention;

FIGS. 23A–E illustrate example signal diagrams associated withdown-converting an analog PM signal to an intermediate frequency signalby under-sampling according to embodiments of the invention;

FIG. 24A illustrates a structural block diagram of a make before breakunder-sampling system according to an embodiment of the invention;

FIG. 24B illustrates an example timing diagram of an under samplingsignal according to an embodiment of the invention;

FIG. 24C illustrates an example timing diagram of an isolation signalaccording to an embodiment of the invention;

FIGS. 25A–H illustrate example aliasing signals at various aliasingrates according to embodiments of the invention;

FIG. 26A illustrates a structural block diagram of an exemplary sampleand hold system according to an embodiment of the invention;

FIG. 26B illustrates a structural block diagram of an exemplary invertedsample and hold system according to an embodiment of the invention;

FIG. 27 illustrates a structural block diagram of sample and hold moduleaccording to an embodiment of the invention;

FIGS. 28A–D illustrate example implementations of a switch moduleaccording to embodiments of the invention;

FIGS. 29A–F illustrate example implementations of a holding moduleaccording to embodiments of the present invention;

FIG. 29G illustrates an integrated under-sampling system according toembodiments of the invention;

FIGS. 29H–K illustrate example implementations of pulse generatorsaccording to embodiments of the invention;

FIG. 29L illustrates an example oscillator;

FIG. 30 illustrates a structural block diagram of an under-samplingsystem with an under-sampling signal optimizer according to embodimentsof the invention;

FIG. 31 illustrates a structural block diagram of an under-samplingsignal optimizer according to embodiments of the present invention;

FIG. 32A illustrates an example of an under-sampling signal moduleaccording to an embodiment of the invention;

FIG. 32B illustrates a flowchart of a state machine operation associatedwith an under-sampling module according to embodiments of the invention;

FIG. 32C illustrates an example under-sampling module that includes ananalog circuit with automatic gain control according to embodiments ofthe invention;

FIGS. 33A–D illustrate example signal diagrams associated with directdown-conversion of an EM signal to a baseband signal by under-samplingaccording to embodiments of the present invention;

FIGS. 34A–F illustrate example signal diagrams associated with aninverted sample and hold module according to embodiments of theinvention;

FIGS. 35A–E illustrate example signal diagrams associated with directlydown-converting an analog AM signal to a demodulated baseband signal byunder-sampling according to embodiments of the invention;

FIGS. 36A–E illustrate example signal diagrams associated withdown-converting a digital AM signal to a demodulated baseband signal byunder-sampling according to embodiments of the invention;

FIGS. 37A–E illustrate example signal diagrams associated with directlydown-converting an analog PM signal to a demodulated baseband signal byunder-sampling according to embodiments of the invention;

FIGS. 38A–E illustrate example signal diagrams associated withdown-converting a digital PM signal to a demodulated baseband signal byunder-sampling according to embodiments of the invention;

FIGS. 39A–D illustrate down-converting a FM signal to a non-FM signal byunder-sampling according to embodiments of the invention;

FIGS. 40A–E illustrate down-converting a FSK signal to a PSK signal byunder-sampling according to embodiments of the invention;

FIGS. 41A–E illustrate down-converting a FSK signal to an ASK signal byunder-sampling according to embodiments of the invention;

FIG. 42 illustrates a structural block diagram of an inverted sample andhold according to an embodiment of the present invention;

FIGS. 43A and 43B illustrate example waveforms present in the circuit ofFIG. 31;

FIG. 44A illustrates a structural block diagram of a differential systemaccording to embodiments of the invention;

FIG. 44B illustrates a structural block diagram of a differential systemwith a differential input and a differential output according toembodiments of the invention;

FIG. 44C illustrates a structural block diagram of a differential systemwith a single input and a differential output according to embodimentsof the invention;

FIG. 44D illustrates a differential input with a single output accordingto embodiments of the invention;

FIG. 44E illustrates an example differential input to single outputsystem according to embodiments of the invention;

FIGS. 45A–B illustrate a conceptual illustration of aliasing includingunder-sampling and energy transfer according to embodiments of theinvention;

FIGS. 46A–D illustrate various flowchart for down-converting an EMsignal by transferring energy from the EM signal at an aliasing rateaccording to embodiments of the invention;

FIGS. 47A–E illustrate example signal diagrams associated with theflowcharts in FIGS. 46A–D according to embodiments of the invention;

FIG. 48 is a flowchart that illustrates an example process fordetermining an aliasing rate associated with an aliasing signalaccording to an embodiment of the invention;

FIG. 49A–H illustrate example energy transfer signals according toembodiments of the invention;

FIGS. 50A–G illustrate example signal diagrams associated withdown-converting an analog AM signal to an intermediate frequency bytransferring energy at an aliasing rate according to embodiments of theinvention;

FIGS. 51A–G illustrate example signal diagrams associated withdown-converting an digital AM signal to an intermediate frequency bytransferring energy at an aliasing rate according to embodiments of theinvention;

FIGS. 52A–G illustrate example signal diagrams associated withdown-converting an analog FM signal to an intermediate frequency bytransferring energy at an aliasing rate according to embodiments of theinvention;

FIGS. 53A–G illustrate example signal diagrams associated withdown-converting an digital FM signal to an intermediate frequency bytransferring energy at an aliasing rate according to embodiments of theinvention;

FIGS. 54A–G illustrate example signal diagrams associated withdown-converting an analog PM signal to an intermediate frequency bytransferring energy at an aliasing rate according to embodiments of theinvention;

FIGS. 55A–G illustrate example signal diagrams associated withdown-converting an digital PM signal to an intermediate frequency bytransferring energy at an aliasing rate according to embodiments of theinvention;

FIGS. 56A–D illustrate an example signal diagram associated with directdown-conversion according to embodiments of the invention;

FIGS. 57A–F illustrate directly down-converting an analog AM signal to ademodulated baseband signal according to embodiments of the invention;

FIGS. 58A–F illustrate directly down-converting an digital AM signal toa demodulated baseband signal according to embodiments of the invention;

FIGS. 59A–F illustrate directly down-converting an analog PM signal to ademodulated baseband signal according to embodiments of the invention;

FIGS. 60A–F illustrate directly down-converting an digital PM signal toa demodulated baseband signal according to embodiments of the invention;

FIGS. 61A–F illustrate down-converting an FM signal to a PM signalaccording to embodiments of the invention;

FIGS. 62A–F illustrate down-converting an FM signal to a AM signalaccording to embodiments of the invention;

FIG. 63 illustrates a block diagram of an energy transfer systemaccording to an embodiment of the invention;

FIG. 64A illustrates an exemplary gated transfer system according to anembodiment of the invention;

FIG. 64B illustrates an exemplary inverted gated transfer systemaccording to an embodiment of the invention;

FIG. 65 illustrates an example embodiment of the gated transfer moduleaccording to an embodiment of the invention;

FIGS. 66A–D illustrate example implementations of a switch moduleaccording to embodiments of the invention;

FIG. 67A illustrates an example embodiment of the gated transfer moduleas including a break-before-make module according to an embodiment ofthe invention;

FIG. 67B illustrates an example timing diagram for an energy transfersignal according to an embodiment of the invention;

FIG. 67C illustrates an example timing diagram for an isolation signalaccording to an embodiment of the invention;

FIGS. 68A–F illustrate example storage modules according to embodimentsof the invention;

FIG. 68G illustrates an integrated gated transfer system according to anembodiment of the invention;

FIGS. 68H–K illustrate example aperture generators;

FIG. 68L illustrates an oscillator according to an embodiment of thepresent invention;

FIG. 69 illustrates an energy transfer system with an optional energytransfer signal module according to an embodiment of the invention;

FIG. 70 illustrates an aliasing module with input and output impedancematch according to an embodiment of the invention;

FIG. 71 illustrates an example pulse generator;

FIGS. 72A and B illustrate example waveforms related to the pulsegenerator of FIG. 71;

FIG. 73 illustrates an example energy transfer module with a switchmodule and a reactive storage module according to an embodiment of theinvention;

FIG. 74 illustrates an example inverted gated transfer module asincluding a switch module and a storage module according to anembodiment of the invention;

FIGS. 75A–F illustrate an example signal diagrams associated with aninverted gated energy transfer module according to embodiments of theinvention;

FIGS. 76A–E illustrate energy transfer modules in configured in variousdifferential configurations according to embodiments of the invention;

FIGS. 77A–C illustrate example impedance matching circuits according toembodiments of the invention;

FIGS. 78A–B illustrate example under-sampling systems according toembodiments of the invention;

FIGS. 79A–F illustrate example timing diagrams for under-samplingsystems according to embodiments of the invention;

FIGS. 80A–E illustrate example timing diagrams for an under-samplingsystem when the load is a relatively low impedance load according toembodiments of the invention;

FIGS. 81A–F illustrate example timing diagrams for an under-samplingsystem when the holding capacitance has a larger value according toembodiments of the invention;

FIGS. 82A–B illustrate example energy transfer systems according toembodiments of the invention;

FIGS. 83A–F illustrate example timing diagrams for energy transfersystems according to embodiments of the present invention;

FIGS. 84A–D illustrate down-converting an FSK signal to a PSK signalaccording to embodiments of the present invention;

FIG. 85A illustrates an example energy transfer signal module accordingto an embodiment of the present invention;

FIG. 85B illustrates a flowchart of state machine operation according toan embodiment of the present invention;

FIG. 85C is an example energy transfer signal module;

FIG. 86 is a schematic diagram of a circuit to down-convert a 915 MHZsignal to a 5 MHZ signal using a 101.1 MHZ clock according to anembodiment of the present invention;

FIG. 87 shows simulation waveforms for the circuit of FIG. 86 accordingto embodiments of the present invention;

FIG. 88 is a schematic diagram of a circuit to down-convert a 915 MHZsignal to a 5 MHz signal using a 101 MHZ clock according to anembodiment of the present invention;

FIG. 89 shows simulation waveforms for the circuit of FIG. 88 accordingto embodiments of the present invention;

FIG. 90 is a schematic diagram of a circuit to down-convert a 915 MHZsignal to a 5 MHZ signal using a 101.1 MHZ clock according to anembodiment of the present invention;

FIG. 91 shows simulation waveforms for the circuit of FIG. 90 accordingto an embodiment of the present invention;

FIG. 92 shows a schematic of the circuit in FIG. 86 connected to an FSKsource that alternates between 913 and 917 MHZ at a baud rate of 500Kbaud according to an embodiment of the present invention;

FIG. 93 shows the original FSK waveform 9202 and the down-convertedwaveform 9204 at the output of the load impedance match circuitaccording to an embodiment of the present invention;

FIG. 94A illustrates an example energy transfer system according to anembodiment of the invention;

FIGS. 94B–C illustrate example timing diagrams for the example system ofFIG. 94A;

FIG. 95 illustrates an example bypass network according to an embodimentof the invention;

FIG. 96 illustrates an example bypass network according to an embodimentof the invention;

FIG. 97 illustrates an example embodiment of the invention;

FIG. 98A illustrates an example real time aperture control circuitaccording to an embodiment of the invention;

FIG. 98B illustrates a timing diagram of an example clock signal forreal time aperture control, according to an embodiment of the invention;

FIG. 98C illustrates a timing diagram of an example optional enablesignal for real time aperture control, according to an embodiment of theinvention;

FIG. 98D illustrates a timing diagram of an inverted clock signal forreal time aperture control, according to an embodiment of the invention;

FIG. 98E illustrates a timing diagram of an example delayed clock signalfor real time aperture control, according to an embodiment of theinvention;

FIG. 98F illustrates a timing diagram of an example energy transferincluding pulses having apertures that are controlled in real time,according to an embodiment of the invention;

FIG. 99 is a block diagram of a differential system that utilizesnon-inverted gated transfer units, according to an embodiment of theinvention;

FIG. 100 illustrates an example embodiment of the invention;

FIG. 101 illustrates an example embodiment of the invention;

FIG. 102 illustrates an example embodiment of the invention;

FIG. 103 illustrates an example embodiment of the invention;

FIG. 104 illustrates an example embodiment of the invention;

FIG. 105 illustrates an example embodiment of the invention;

FIG. 106 illustrates an example embodiment of the invention;

FIG. 107A is a timing diagram for the example embodiment of FIG. 103;

FIG. 107B is a timing diagram for the example embodiment of FIG. 104;

FIG. 108A is a timing diagram for the example embodiment of FIG. 105;

FIG. 108B is a timing diagram for the example embodiment of FIG. 106;

FIG. 109A illustrates and example embodiment of the invention;

FIG. 109B illustrates equations for determining charge transfer, inaccordance with the present invention;

FIG. 109C illustrates relationships between capacitor charging andaperture, in accordance with the present invention;

FIG. 109D illustrates relationships between capacitor charging andaperture, in accordance with the present invention;

FIG. 109E illustrates power-charge relationship equations, in accordancewith the present invention;

FIG. 109F illustrates insertion loss equations, in accordance with thepresent invention;

FIG. 110A illustrates aliasing module 11000 a single FET configuration;

FIG. 110B illustrates FET conductivity vs. V_(GS);

FIGS. 111A–C illustrate signal waveforms associated with aliasing module11000;

FIG. 112 illustrates aliasing module 11200 with a complementary FETconfiguration;

FIGS. 113A–E illustrate signal waveforms associated with aliasing module11200;

FIG. 114 illustrates aliasing module 11400;

FIG. 115 illustrates aliasing module 11500;

FIG. 116 illustrates aliasing module 11602;

FIG. 117 illustrates aliasing module 11702;

FIGS. 118–120 illustrate signal waveforms associated with aliasingmodule 11602;

FIGS. 121–123 illustrate signal waveforms associated with aliasingmodule 11702.

FIG. 124A is a block diagram of a splitter according to an embodiment ofthe invention;

FIG. 124B is a more detailed diagram of a splitter according to anembodiment of the invention;

FIGS. 124C and 124D are example waveforms related to the splitter ofFIGS. 124A and 124B;

FIG. 124E is a block diagram of an I/Q circuit with a splitter accordingto an embodiment of the invention;

FIGS. 124F–124J are example waveforms related to the diagram of FIG.124A;

FIG. 125 is a block diagram of a switch module according to anembodiment of the invention;

FIG. 126A is an implementation example of the block diagram of FIG. 125;

FIGS. 126B–126Q are example waveforms related to FIG. 126A;

FIG. 127A is another implementation example of the block diagram of FIG.125;

FIGS. 127B–127Q are example waveforms related to FIG. 127A;

FIG. 128A is an example MOSFET embodiment of the invention;

FIG. 128B is an example MOSFET embodiment of the invention;

FIG. 128C is an example MOSFET embodiment of the invention;

FIG. 129A is another implementation example of the block diagram of FIG.125;

FIGS. 129B–129Q are example waveforms related to FIG. 127A;

FIGS. 130 and 131 illustrate the amplitude and pulse width modulatedtransmitter according to embodiments of the present invention;

FIGS. 132A–132D illustrate example signal diagrams associated with theamplitude and pulse width modulated transmitter according to embodimentsof the present invention;

FIG. 133 illustrates an example diagram associated with the amplitudeand pulse width modulated transmitter according to embodiments of thepresent invention;

FIG. 134 illustrates an example diagram associated with the amplitudeand pulse width modulated transmitter according to embodiments of thepresent invention;

FIG. 135 shows an embodiment of a receiver block diagram to recover theamplitude or pulse width modulated information;

FIGS. 136A–136G illustrate example signal diagrams associated with awaveform generator according to embodiments of the present invention;

FIGS. 137–139 are example schematic diagrams illustrating variouscircuits employed in the receiver of FIG. 135;

FIGS. 140–143 illustrate time and frequency domain diagrams ofalternative transmitter output waveforms;

FIGS. 144 and 145 illustrate differential receivers in accord withembodiments of the present invention; and

FIGS. 146 and 147 illustrate time and frequency domains for a narrowbandwidth/constant carrier signal in accord with an embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION Table of Contents

FIELD OF THE INVENTION

Related Art

Table of Contents

-   I. Introduction    -   1. General Terminology        -   1.1 Modulation            -   1.1.1 Amplitude Modulation            -   1.1.2 Frequency Modulation            -   1.1.3 Phase Modulation        -   1.2 Demodulation    -   2. Overview of the Invention        -   2.1 Aspects of the Invention        -   2.2 Down-Converting by Under-Sampling            -   2.2.1 Down-Converting to an Intermediate Frequency (IF)                Signal            -   2.2.2 Direct-to-Data Down-Converting            -   2.2.3 Modulation Conversion        -   2.3 Down-Converting by Transferring Energy            -   2.3.1 Down-Converting to an Intermediate Frequency (IF)                Signal            -   2.3.2 Direct-to-Data Down-Converting            -   2.3.3 Modulation Conversion        -   2.4 Determining the Aliasing Rate    -   3. Benefits of the Invention Using an Example Conventional        Receiver for Comparison-   II. Down-Converting by Under-Sampling    -   1. Down-Converting an EM Carrier Signal to an EM Intermediate        Signal by Under-Sampling the EM Carrier Signal at the Aliasing        Rate        -   1.1 High Level Description            -   1.1.1 Operational Description            -   1.1.2 Structural Description        -   1.1 Example Embodiments            -   1.2.1 First Example Embodiment: Amplitude Modulation                -   1.2.1.1 Operational Description                -    1.2.1.1.1 AnalogAMCarrierSignal                -    1.2.1.1.2 Digital AM Carrier Signal                -   1.2.1.2 Structural Description            -   1.2.2 Second Example Embodiment: Frequency Modulation                -   1.2.2.1 Operational Description                -    1.2.2.1.1 Analog FM Carrier Signal                -    1.2.2.1.2 Digital FM Carrier Signal                -   1.2.2.2 Structural Description            -   1.2.3 Third Example Embodiment: Phase Modulation                -   1.2.3.1 Operational Description                -    1.2.3.1.1 Analog PM Carrier Signal                -    1.2.3.1.2 Digital PM Carrier Signal                -   1.2.3.2 Structural Description            -   1.2.4 Other Embodiments        -   1.3 Implementation Examples    -   2. Directly Down-Converting an EM Signal to a Baseband Signal        (Direct-to-Data)        -   2.1 High Level Description            -   2.1.1 Operational Description            -   2.1.2 Structural Description        -   2.2 Example Embodiments            -   2.2.1 First Example Embodiment: Amplitude Modulation                -   2.2.1.1 Operational Description                -    2.2.1.1.1 Analog AM Carrier Signal                -    2.2.1.1.2 Digital AM Carrier Signal                -   2.2.1.2 Structural Description            -   2.2.2 Second Example Embodiment: Phase Modulation                -   2.2.2.1 Operational Description                -    2.2.2.1.1 Analog PM Carrier Signal                -    2.2.2.1.2 Digital PM Carrier Signal                -   2.2.1.2 Structural Description            -   2.2.3 Other Embodiments        -   2.3 Implementation Examples    -   3. Modulation Conversion        -   3.1 High Level Description            -   3.1.1 Operational Description            -   3.1.2 Structural Description        -   3.2 Example Embodiments            -   3.2.1 First Example Embodiment: Down-Converting an FM                Signal to a PM Signal                -   3.2.1.1 Operational Description                -   3.2.1.2 Structural Description            -   3.2.2 Second Example Embodiment: Down-Converting an FM                Signal to an AM Signal                -   3.2.2.1 Operational Description                -   3.2.2.2 Structural Description            -   3.2.3 Other Example Embodiments        -   3.3 Implementation Examples    -   4. Implementation Examples        -   4.1 The Under-Sampling System as a Sample and Hold System            -   4.1.1 The Sample and Hold System as a Switch Module and                a Holding Module            -   4.1.2 The Sample and Hold System as Break-Before-Make                Module            -   4.1.3 Example Implementations of the Switch Module            -   4.1.4 Example Implementations of the Holding Module            -   4.1.5 Optional Under-Sampling Signal Module        -   4.2 The Under-Sampling System as an Inverted Sample and Hold        -   4.3 Other Implementations    -   5. Optional Optimizations of Under-Sampling at an Aliasing Rate        -   5.1 Doubling the Aliasing Rate (F_(AR)) of the            Under-Sampling Signal        -   5.2 Differential Implementations            -   5.2.1 Differential Input-to-Differential Output            -   5.2.2 Single Input-to-Differential Output            -   5.2.3 Differential Input-to-Single Output        -   5.3 Smoothing the Down-Converted Signal        -   5.4 Load Impedance and Input/Output Buffering        -   5.5 Modifying the Under-Sampling Signal Utilizing Feedback-   III. Down-Converting by Transferring Energy    -   1. Energy Transfer Compared to Under-Sampling        -   1.1 Review of Under-Sampling            -   1.1.1 Effects of Lowering the Impedance of the Load            -   1.1.2 Effects of Increasing the Value of the Holding                Capacitance        -   1.2 Introduction to Energy Transfer    -   2. Down-Converting an EM Signal to an IF EM Signal by        Transferring Energy from the EM Signal at an Aliasing Rate        -   2.1 High Level Description            -   2.1.1 Operational Description        -   2.2 Example Embodiments            -   2.2.1 First Example Embodiment: Amplitude Modulation                -   2.2.1.1 Operational Description                -    2.2.1.1.1 Analog AM Carrier Signal                -    2.2.1.2.2 Digital AM Carrier Signal                -   2.2.1.2 Structural Description            -   2.2.2 Second Example Embodiment: Frequency Modulation                -   2.2.2.1 Operational Description                -    2.2.2.1.1 Analog FM Carrier Signal                -    2.2.2.1.2 Digital FM Carrier Signal                -   2.2.2.2 Structural Description            -   2.2.3 Third Example Embodiment: Phase Modulation                -   2.2.3.1 Operational Description                -    2.2.3.1.1 Analog PM Carrier Signal                -    2.2.3.1.2 Digital PM Carrier Signal                -   2.2.3.2 Structural Description            -   2.2.4 Other Embodiments        -   2.3 Implementation Examples    -   3. Directly Down-Converting an EM Signal to an Demodulated        Baseband Signal by Transferring Energy from the EM Signal        -   3.1 High Level Description            -   3.1.1 Operational Description            -   3.1.2 Structural Description        -   3.2 Example Embodiments            -   3.2.1 First Example Embodiment: Amplitude Modulation                -   3.2.1.1 Operational Description                -    3.2.1.1.1 Analog AM Carrier Signal                -    3.2.1.1.2 Digital AM Carrier Signal                -   3.2.1.2 Structural Description            -   3.2.2 Second Example Embodiment: Phase Modulation                -   3.2.2.1 Operational Description                -    3.2.2.1.1 Analog PM Carrier Signal                -    3.2.2.1.2 Digital PM Carrier Signal                -   3.2.2.2 Structural Description            -   3.2.3 Other Embodiments        -   3.3 Implementation Examples    -   4. Modulation Conversion        -   4.1 High Level Description            -   4.1.1 Operational Description            -   4.1.2 Structural Description        -   4.2 Example Embodiments            -   4.2.1 First Example Embodiment: Down-Converting an FM                Signal to a PM Signal                -   4.2.1.1 Operational Description                -   4.2.1.2 Structural Description            -   4.2.2 Second Example Embodiment: Down-Converting an FM                Signal to an AM Signal                -   4.2.2.1 Operational Description                -   4.2.2.2 Structural Description            -   4.2.3 Other Example Embodiments        -   4.3 Implementation Examples    -   5. Implementation Examples        -   5.1 The Energy Transfer System as a Gated Transfer System            -   5.1.1 The Gated Transfer System as a Switch Module and a                Storage Module            -   5.1.2 The Gated Transfer System as Break-Before-Make                Module            -   5.1.3 Example Implementations of the Switch Module            -   5.1.4 Example Implementations of the Storage Module            -   5.1.5 Optional Energy Transfer Signal Module        -   5.2 The Energy Transfer System as an Inverted Gated Transfer            System            -   5.2.1 The Inverted Gated Transfer System as a Switch                Module and a Storage Module        -   5.3 Rail to Rail Operation for Improved Dynamic Range            -   5.3.1 Introduction            -   5.3.2 Complementary UFT Structure for Improved Dynamic                Range            -   5.3.3 Biased Configurations            -   5.3.4 Simulation Examples        -   5.4 Optimized Switch Structures            -   5.4.1 Splitter in CMOS            -   5.4.2 I/Q Circuit        -   5.5 Example I and Q Implementations            -   5.5.1 Switches of Different Sizes            -   5.5.2 Reducing Overall Switch Area            -   5.5.3 Charge Injection Cancellation            -   5.5.4 Overlapped Capacitance        -   5.6 Other Implementations    -   6. Optional Optimizations of Energy Transfer at an Aliasing Rate        -   6.1 Doubling the Aliasing Rate (F_(AR)) of the Energy            Transfer Signal        -   6.2 Differential Implementations            -   6.2.1 An Example Illustrating Energy Transfer                Differentially                -   6.2.1.1 Differential Input-to-Differential Output                -   6.2.1.2 Single Input-to-Differential Output                -   6.2.1.3 Differential Input-to-Single Output            -   6.2.2 Specific Alternative Embodiments            -   6.2.3 Specific Examples of Optimizations and                Configurations for Inverted and Non-Inverted                Differential Designs        -   6.3 Smoothing the Down-Converted Signal        -   6.4 Impedance Matching        -   6.5 Tanks and Resonant Structures        -   6.6 Charge and Power Transfer Concepts        -   6.7 Optimizing and Adjusting the Non-Negligible Aperture            Width/Duration            -   6.7.1 Varying Input and Output Impedances            -   6.7.2 Real Time Aperture Control        -   6.8 Adding a Bypass Network        -   6.9 Modifying the Energy Transfer Signal Utilizing Feedback        -   6.10 Other Implementations    -   7. Example Energy Transfer Downconverters-   IV. Additional Embodiments-   V. Conclusions    I. Introduction

1. General Terminology

For illustrative purposes, the operation of the invention is oftenrepresented by flowcharts, such as flowchart 1201 in FIG. 12A. It shouldbe understood, however, that the use of flowcharts is for illustrativepurposes only, and is not limiting. For example, the invention is notlimited to the operational embodiment(s) represented by the flowcharts.Instead, alternative operational embodiments will be apparent to personsskilled in the relevant art(s) based on the discussion contained herein.Also, the use of flowcharts should not be interpreted as limiting theinvention to discrete or digital operation. In practice, as will beappreciated by persons skilled in the relevant art(s) based on theherein discussion, the invention can be achieved via discrete orcontinuous operation, or a combination thereof. Further, the flow ofcontrol represented by the flowcharts is provided for illustrativepurposes only. As will be appreciated by persons skilled in the relevantart(s), other operational control flows are within the scope and spiritof the present invention. Also, the ordering of steps may differ invarious embodiments.

Various terms used in this application are generally described in thissection. The description in this section is provided for illustrativeand convenience purposes only, and is not limiting. The meaning of theseterms will be apparent to persons skilled in the relevant art(s) basedon the entirety of the teachings provided herein. These terms may bediscussed throughout the specification with additional detail.

The term modulated carrier signal, when used herein, refers to a carriersignal that is modulated by a baseband signal.

The term unmodulated carrier signal, when used herein, refers to asignal having an amplitude that oscillates at a substantially uniformfrequency and phase.

The term baseband signal, when used herein, refers to an informationsignal including, but not limited to, analog information signals,digital information signals and direct current (DC) information signals.

The term carrier signal, when used herein, and unless otherwisespecified when used herein, refers to modulated carrier signals andunmodulated carrier signals.

Information signals, digital information signals and direct current (DC)information signals.

The term electromagnetic (EM) signal, when used herein, refers to asignal in the EM spectrum. EM spectrum includes all frequencies greaterthan zero hertz. EM signals generally include waves characterized byvariations in electric and magnetic fields. Such waves may be propagatedin any medium, both natural and manmade, including but not limited toair, space, wire, cable, liquid, waveguide, micro-strip, strip-line,optical fiber, etc. Unless stated otherwise, all signals discussedherein are EM signals, even when not explicitly designated as such.

The term intermediate frequency (IF) signal, when used herein, refers toan EM signal that is substantially similar to another EM signal exceptthat the IF signal has a lower frequency than the other signal. An IFsignal frequency can be any frequency above zero HZ. Unless otherwisestated, the terms lower frequency, intermediate frequency, intermediateand IF are used interchangeably herein.

The term analog signal, when used herein, refers to a signal that isconstant or continuously variable, as contrasted to a signal thatchanges between discrete states.

The term baseband, when used herein, refers to a frequency band occupiedby any generic information signal desired for transmission and/orreception.

The term baseband signal, when used herein, refers to any genericinformation signal desired for transmission and/or reception.

The term carrier frequency, when used herein, refers to the frequency ofa carrier signal. Typically, it is the center frequency of atransmission signal that is generally modulated.

The term carrier signal, when used herein, refers to an EM wave havingat least one characteristic that may be varied by modulation, that iscapable of carrying information via modulation.

The term demodulated baseband signal, when used herein, refers to asignal that results from processing a modulated signal. In some cases,for example, the demodulated baseband signal results from demodulatingan intermediate frequency (IF) modulated signal, which results from downconverting a modulated carrier signal. In another case, a signal thatresults from a combined downconversion and demodulation step.

The term digital signal, when used herein, refers to a signal thatchanges between discrete states, as contrasted to a signal that iscontinuous. For example, the voltage of a digital signal may shiftbetween discrete levels.

The term electromagnetic (EM) spectrum, when used herein, refers to aspectrum comprising waves characterized by variations in electric andmagnetic fields. Such waves may be propagated in any communicationmedium, both natural and manmade, including but not limited to air,space, wire, cable, liquid, waveguide, microstrip, stripline, opticalfiber, etc. The EM spectrum includes all frequencies greater than zerohertz.

The term electromagnetic (EM) signal, when used herein, refers to asignal in the EM spectrum. Also generally called an EM wave. Unlessstated otherwise, all signals discussed herein are EM signals, even whennot explicitly designated as such.

The term modulating baseband signal, when used herein, refers to anygeneric information signal that is used to modulate an oscillatingsignal, or carrier signal.

-   -   1.1 Modulation

It is often beneficial to propagate electromagnetic (EM) signals athigher frequencies. This includes baseband signals, such as digital datainformation signals and analog information signals. A baseband signalcan be up-converted to a higher frequency EM signal by using thebaseband signal to modulate a higher frequency carrier signal, F_(C).When used in this manner, such a baseband signal is herein called amodulating baseband signal F_(MB).

Modulation imparts changes to the carrier signal F_(C) that representinformation in the modulating baseband signal F_(MB). The changes can bein the form of amplitude changes, frequency changes, phase changes,etc., or any combination thereof. The resultant signal is referred toherein as a modulated carrier signal F_(MC). The modulated carriersignal F_(MC) includes the carrier signal F_(C) modulated by themodulating baseband signal, F_(MB), as in:F_(MB) combined with F_(C)→F_(MC)The modulated carrier signal F_(MC) oscillates at, or near the frequencyof the carrier signal F_(C) and can thus be efficiently propagated.

FIG. 1 illustrates an example modulator 110, wherein the carrier signalF_(C) is modulated by the modulating baseband signal F_(MB), therebygenerating the modulated carrier signal F_(MC).

Modulating baseband signal F_(MB) can be an analog baseband signal, adigital baseband signal, or a combination thereof.

FIG. 2 illustrates the modulating baseband signal F_(MB) as an exemplaryanalog modulating baseband signal 210. The exemplary analog modulatingbaseband signal 210 can represent any type of analog informationincluding, but not limited to, voice/speech data, music data, videodata, etc. The amplitude of analog modulating baseband signal 210 variesin time.

Digital information includes a plurality of discrete states. For ease ofexplanation, digital information signals are discussed below as havingtwo discrete states. But the invention is not limited to thisembodiment.

FIG. 3 illustrates the modulating baseband signal F_(MB) as an exemplarydigital modulating baseband signal 310. The digital modulating basebandsignal 310 can represent any type of digital data including, but notlimited to, digital computer information and digitized analoginformation. The digital modulating baseband signal 310 includes a firststate 312 and a second state 314. In an embodiment, first state 312represents binary state 0 and second state 314 represents binarystate 1. Alternatively, first state 312 represents binary state 1 andsecond state 314 represents binary state 0. Throughout the remainder ofthis disclosure, the former convention is followed, whereby first state312 represents binary state zero and second state 314 represents binarystate one. But the invention is not limited to this embodiment. Firststate 312 is thus referred to herein as a low state and second state 314is referred to herein as a high state.

Digital modulating baseband signal 310 can change between first state312 and second state 314 at a data rate, or baud rate, measured as bitsper second.

Carrier signal F_(C) is modulated by the modulating baseband signalF_(MB), by any modulation technique, including, but not limited to,amplitude modulation (AM), frequency modulation (FM), phase modulation(PM), etc., or any combination thereof. Examples are provided below foramplitude modulating, frequency modulating, and phase modulating theanalog modulating baseband signal 210 and the digital modulatingbaseband signal 310, on the carrier signal F_(C). The examples are usedto assist in the description of the invention. The invention is notlimited to, or by, the examples.

FIG. 4 illustrates the carrier signal F_(C) as a carrier signal 410. Inthe example of FIG. 4, the carrier signal 410 is illustrated as a 900MHZ carrier signal. Alternatively, the carrier signal 410 can be anyother frequency. Example modulation schemes are provided below, usingthe examples signals from FIGS. 2, 3 and 4.

-   -   -   1.1.1 Amplitude Modulation

In amplitude modulation (AM), the amplitude of the modulated carriersignal F_(MC) is a function of the amplitude of the modulating basebandsignal F_(MB). FIGS. 5A–5C illustrate example timing diagrams foramplitude modulating the carrier signal 410 with the analog modulatingbaseband signal 210. FIGS. 6A–6C illustrate example timing diagrams foramplitude modulating the carrier signal 410 with the digital modulatingbaseband signal 310.

FIG. 5A illustrates the analog modulating baseband signal 210. FIG. 5Billustrates the carrier signal 410. FIG. 5C illustrates an analog AMcarrier signal 516, which is generated when the carrier signal 410 isamplitude modulated using the analog modulating baseband signal 210. Asused herein, the term “analog AM carrier signal” is used to indicatethat the modulating baseband signal is an analog signal.

The analog AM carrier signal 516 oscillates at the frequency of carriersignal 410. The amplitude of the analog AM carrier signal 516 tracks theamplitude of analog modulating baseband signal 210, illustrating thatthe information contained in the analog modulating baseband signal 210is retained in the analog AM carrier signal 516.

FIG. 6A illustrates the digital modulating baseband signal 310. FIG. 6Billustrates the carrier signal 410. FIG. 6C illustrates a digital AMcarrier signal 616, which is generated when the carrier signal 410 isamplitude modulated using the digital modulating baseband signal 310. Asused herein, the term “digital AM carrier signal” is used to indicatethat the modulating baseband signal is a digital signal.

The digital AM carrier signal 616 oscillates at the frequency of carriersignal 410. The amplitude of the digital AM carrier signal 616 tracksthe amplitude of digital modulating baseband signal 310, illustratingthat the information contained in the digital modulating baseband signal310 is retained in the digital AM signal 616. As the digital modulatingbaseband signal 310 changes states, the digital AM signal 616 shiftsamplitudes. Digital amplitude modulation is often referred to asamplitude shift keying (ASK), and the two terms are used interchangeablythroughout the specification.

-   -   -   1.1.2 Frequency Modulation

In frequency modulation (FM), the frequency of the modulated carriersignal F_(MC) varies as a function of the amplitude of the modulatingbaseband signal F_(MB). FIGS. 7A–7C illustrate example timing diagramsfor frequency modulating the carrier signal 410 with the analogmodulating baseband signal 210. FIGS. 8A–8C illustrate example timingdiagrams for frequency modulating the carrier signal 410 with thedigital modulating baseband signal 310.

FIG. 7A illustrates the analog modulating baseband signal 210. FIG. 7Billustrates the carrier signal 410. FIG. 7C illustrates an analog FMcarrier signal 716, which is generated when the carrier signal 410 isfrequency modulated using the analog modulating baseband signal 210. Asused herein, the term “analog FM carrier signal” is used to indicatethat the modulating baseband signal is an analog signal.

The frequency of the analog FM carrier signal 716 varies as a functionof amplitude changes on the analog baseband signal 210. In theillustrated example, the frequency of the analog FM carrier signal 716varies in proportion to the amplitude of the analog modulating basebandsignal 210. Thus, at time t1, the amplitude of the analog basebandsignal 210 and the frequency of the analog FM carrier signal 716 are atmaximums. At time t3, the amplitude of the analog baseband signal 210and the frequency of the analog FM carrier signal 716 are at minimums.

The frequency of the analog FM carrier signal 716 is typically centeredaround the frequency of the carrier signal 410. Thus, at time t2, forexample, when the amplitude of the analog baseband signal 210 is at amid-point, illustrated here as zero volts, the frequency of the analogFM carrier signal 716 is substantially the same as the frequency of thecarrier signal 410.

FIG. 8A illustrates the digital modulating baseband signal 310. FIG. 8Billustrates the carrier signal 410. FIG. 8C illustrates a digital FMcarrier signal 816, which is generated when the carrier signal 410 isfrequency modulated using the digital baseband signal 310. As usedherein, the term “digital FM carrier signal” is used to indicate thatthe modulating baseband signal is a digital signal.

The frequency of the digital FM carrier signal 816 varies as a functionof amplitude changes on the digital modulating baseband signal 310. Inthe illustrated example, the frequency of the digital FM carrier signal816 varies in proportion to the amplitude of the digital modulatingbaseband signal 310. Thus, between times t0 and t1, and between times t2and t4, when the amplitude of the digital baseband signal 310 is at thehigher amplitude second state, the frequency of the digital FM carriersignal 816 is at a maximum. Between times t1 and t2, when the amplitudeof the digital baseband signal 310 is at the lower amplitude firststate, the frequency of the digital FM carrier signal 816 is at aminimum. Digital frequency modulation is often referred to as frequencyshift keying (FSK), and the terms are used interchangeably throughoutthe specification.

Typically, the frequency of the digital FM carrier signal 816 iscentered about the frequency of the carrier signal 410, and the maximumand minimum frequencies are equally offset from the center frequency.Other variations can be employed but, for ease of illustration, thisconvention will be followed herein.

-   -   -   1.1.3 Phase Modulation

In phase modulation (PM), the phase of the modulated carrier signalF_(MC) varies as a function of the amplitude of the modulating basebandsignal F_(MB). FIGS. 9A–9C illustrate example timing diagrams for phasemodulating the carrier signal 410 with the analog modulating basebandsignal 210. FIGS. 10A–10C illustrate example timing diagrams for phasemodulating the carrier signal 410 with the digital modulating basebandsignal 310.

FIG. 9A illustrates the analog modulating baseband signal 210. FIG. 9Billustrates the carrier signal 410. FIG. 9C illustrates an analog PMcarrier signal 916, which is generated by phase modulating the carriersignal 410 with the analog baseband signal 210. As used herein, the term“analog PM carrier signal” is used to indicate that the modulatingbaseband signal is an analog signal.

Generally, the frequency of the analog PM carrier signal 916 issubstantially the same as the frequency of carrier signal 410. But thephase of the analog PM carrier signal 916 varies with amplitude changeson the analog modulating baseband signal 210. For relative comparison,the carrier signal 410 is illustrated in FIG. 9C by a dashed line.

The phase of the analog PM carrier signal 916 varies as a function ofamplitude changes of the analog baseband signal 210. In the illustratedexample, the phase of the analog PM signal 916 lags by a varying amountas determined by the amplitude of the baseband signal 210. For example,at time t1, when the amplitude of the analog baseband signal 210 is at amaximum, the analog PM carrier signal 916 is in phase with the carriersignal 410. Between times t1 and t3, when the amplitude of the analogbaseband signal 210 decreases to a minimum amplitude, the phase of theanalog PM carrier signal 916 lags the phase of the carrier signal 410,until it reaches a maximum out of phase value at time t3. In theillustrated example, the phase change is illustrated as approximately180 degrees. Any suitable amount of phase change, varied in any mannerthat is a function of the baseband signal, can be utilized.

FIG. 10A illustrates the digital modulating baseband signal 310. FIG.10B illustrates the carrier signal 410. FIG. 10C illustrates a digitalPM carrier signal 1016, which is generated by phase modulating thecarrier signal 410 with the digital baseband signal 310. As used herein,the term “digital PM carrier signal” is used to indicate that themodulating baseband signal is a digital signal.

The frequency of the digital PM carrier signal 1016 is substantially thesame as the frequency of carrier signal 410. The phase of the digital PMcarrier signal 1016 varies as a function of amplitude changes on thedigital baseband signal 310. In the illustrated example, when thedigital baseband signal 310 is at the first state 312, the digital PMcarrier signal 1016 is out of phase with the carrier signal 410. Whenthe digital baseband signal 310 is at the second state 314, the digitalPM carrier signal 1016 is in-phase with the carrier signal 410. Thus,between times t1 and t2, when the amplitude of the digital basebandsignal 310 is at the first state 312, the digital PM carrier signal 1016is out of phase with the carrier signal 410. Between times t0 and t1,and between times t2 and t4, when the amplitude of the digital basebandsignal 310 is at the second state 314, the digital PM carrier signal1016 is in phase with the carrier signal 410.

In the illustrated example, the out of phase value between times t1 andt3 is illustrated as approximately 180 degrees out of phase. Anysuitable amount of phase change, varied in any manner that is a functionof the baseband signal, can be utilized. Digital phase modulation isoften referred to as phase shift keying (PSK), and the terms are usedinterchangeably throughout the specification.

-   -   1.2 Demodulation

When the modulated carrier signal F_(MC) is received, it can bedemodulated to extract the modulating baseband signal F_(MB). Because ofthe typically high frequency of modulated carrier signal F_(MC),however, it is generally impractical to demodulate the baseband signalF_(MB) directly from the modulated carrier signal F_(MC). Instead, themodulated carrier signal F_(MC) must be down-converted to a lowerfrequency signal that contains the original modulating baseband signal.

When a modulated carrier signal is down-converted to a lower frequencysignal, the lower frequency signal is referred to herein as anintermediate frequency (IF) signal F_(IF). The IF signal F_(IF)oscillates at any frequency, or frequency band, below the frequency ofthe modulated carrier frequency FMC. Down-conversion of F_(MC) to F_(IF)is illustrated as:F_(MC)→F_(IF)

After F_(MC) is down-converted to the IF modulated carrier signalF_(IF), F_(IF) can be demodulated to a baseband signal F_(DMB), asillustrated by:F_(IF)→F_(DMB)F_(DMB) is intended to be substantially similar to the modulatingbaseband signal F_(MB), illustrating that the modulating baseband signalF_(MB) can be substantially recovered.

It will be emphasized throughout the disclosure that the presentinvention can be implemented with any type of EM signal, including, butnot limited to, modulated carrier signals and unmodulated carriersignals. The above examples of modulated carrier signals are providedfor illustrative purposes only. Many variations to the examples arepossible. For example, a carrier signal can be modulated with aplurality of the modulation types described above. A carrier signal canalso be modulated with a plurality of baseband signals, including analogbaseband signals, digital baseband signals, and combinations of bothanalog and digital baseband signals.

2. Overview of the Invention

Conventional signal processing techniques follow the Nyquist samplingtheorem, which states that, in order to faithfully reproduce a sampledsignal, the signal must be sampled at a rate that is greater than twicethe frequency of the signal being sampled. When a signal is sampled atless than or equal to twice the frequency of the signal, the signal issaid to be under-sampled, or aliased. Conventional signal processingthus teaches away from under-sampling and aliasing, in order tofaithfully reproduce a sampled signal.

-   -   2.1 Aspects of the Invention

Contrary to conventional wisdom, the present invention is a method andsystem for down-converting an electromagnetic (EM) signal by aliasingthe EM signal. Aliasing is represented generally in FIG. 45A as 4502.

By taking a carrier and aliasing it at an aliasing rate, the inventioncan down-convert that carrier to lower frequencies. One aspect that canbe exploited by this invention is realizing that the carrier is not theitem of interest, the lower baseband signal is of interest to reproducesufficiently. This baseband signal's frequency content, even though itscarrier may be aliased, does satisfy the Nyquist criteria and as aresult, the baseband information can be sufficiently reproduced.

FIG. 12A depicts a flowchart 1201 that illustrates a method for aliasingan EM signal to generate a down-converted signal. The process begins atstep 1202, which includes receiving the EM signal. Step 1204 includesreceiving an aliasing signal having an aliasing rate. Step 1206 includesaliasing the EM signal to down-convert the EM signal. The term aliasing,as used herein, refers to both down-converting an EM signal byunder-sampling the EM signal at an aliasing rate and to down-convertingan EM signal by transferring energy from the EM signal at the aliasingrate. These concepts are described below.

FIG. 13 illustrates a block diagram of a generic aliasing system 1302,which includes an aliasing module 1306. In an embodiment, the aliasingsystem 1302 operates in accordance with the flowchart 1201. For example,in step 1202, the aliasing module 1306 receives an EM signal 1304. Instep 1204, the aliasing module 1306 receives an aliasing signal 1310. Instep 1206, the aliasing module 1306 down-converts the EM signal 1304 toa down-converted signal 1308. The generic aliasing system 1302 can alsobe used to implement any of the flowcharts 1207, 1213 and 1219.

In an embodiment, the invention down-converts the EM signal to anintermediate frequency (IF) signal. FIG. 12B depicts a flowchart 1207that illustrates a method for under-sampling the EM signal at analiasing rate to down-convert the EM signal to an IF signal. The processbegins at step 1208, which includes receiving an EM signal. Step 1210includes receiving an aliasing signal having an aliasing rate F_(AR).Step 1212 includes under-sampling the EM signal at the aliasing rate todown-convert the EM signal to an IF signal.

In another embodiment, the invention down-converts the EM signal to ademodulated baseband information signal. FIG. 12C depicts a flowchart1213 that illustrates a method for down-converting the EM signal to ademodulated baseband signal. The process begins at step 1214, whichincludes receiving an EM signal. Step 1216 includes receiving analiasing signal having an aliasing rate F_(AR). Step 1218 includesdown-converting the EM signal to a demodulated baseband signal. Thedemodulated baseband signal can be processed without furtherdown-conversion or demodulation.

In another embodiment, the EM signal is a frequency modulated (FM)signal, which is down-converted to a non-FM signal, such as a phasemodulated (PM) signal or an amplitude modulated (AM) signal. FIG. 12Ddepicts a flowchart 1219 that illustrates a method for down-convertingthe FM signal to a non-FM signal. The process begins at step 1220, whichincludes receiving an EM signal. Step 1222 includes receiving analiasing signal having an aliasing rate. Step 1224 includesdown-converting the FM signal to a non-FM signal.

The invention down-converts any type of EM signal, including, but notlimited to, modulated carrier signals and unmodulated carrier signals.For ease of discussion, the invention is further described herein usingmodulated carrier signals for examples. Upon reading the disclosure andexamples therein, one skilled in the relevant art(s) will understandthat the invention can be implemented to down-convert signals other thancarrier signals as well. The invention is not limited to the exampleembodiments described above.

In an embodiment, down-conversion is accomplished by under-sampling anEM signal. This is described generally in Section I.2.2. below and indetail in Section II and its sub-sections. In another embodiment,down-conversion is achieved by transferring non-negligible amounts ofenergy from an EM signal. This is described generally in Section I.2.3.below and in detail in Section III.

-   -   2.2 Down-Converting by Under-Sampling

The term aliasing, as used herein, refers both to down-converting an EMsignal by under-sampling the EM signal at an aliasing rate and todown-converting an EM signal by transferring energy from the EM signalat the aliasing rate. Methods for under-sampling an EM signal todown-convert the EM signal are now described at an overview level. FIG.14A depicts a flowchart 1401 that illustrates a method forunder-sampling the EM signal at an aliasing rate to down-convert the EMsignal. The process begins at step 1402, which includes receiving an EMsignal. Step 1404 includes receiving an under-sampling signal having analiasing rate. Step 1406 includes under-sampling the EM signal at thealiasing rate to down-convert the EM signal.

Down-converting by under-sampling is illustrated by 4504 in FIG. 45A andis described in greater detail in Section II.

-   -   -   2.2.1 Down-Converting to an Intermediate Frequency (IF)            Signal

In an embodiment, an EM signal is under-sampled at an aliasing rate todown-convert the EM signal to a lower, or intermediate frequency (IF)signal. The EM signal can be a modulated carrier signal or anunmodulated carrier signal. In an exemplary example, a modulated carriersignal F_(MC) is down-converted to an IF signal F_(IF).F_(MC)→F_(IF)

FIG. 14B depicts a flowchart 1407 that illustrates a method forunder-sampling the EM signal at an aliasing rate to down-convert the EMsignal to an IF signal. The process begins at step 1408, which includesreceiving an EM signal. Step 1410 includes receiving an under-samplingsignal having an aliasing rate. Step 1412 includes under-sampling the EMsignal at the aliasing rate to down-convert the EM signal to an IFsignal.

This embodiment is illustrated generally by 4508 in FIG. 45B and isdescribed in Section II.1.

-   -   -   2.2.2 Direct-to-Data Down-Converting

In another embodiment, an EM signal is directly down-converted to ademodulated baseband signal (direct-to-data down-conversion), byunder-sampling the EM signal at an aliasing rate. The EM signal can be amodulated EM signal or an unmodulated EM signal. In an exemplaryembodiment, the EM signal is the modulated carrier signal F_(MC), and isdirectly down-converted to a demodulated baseband signal F_(DMB).F_(MC)→F_(DMB)

FIG. 14C depicts a flowchart 1413 that illustrates a method forunder-sampling the EM signal at an aliasing rate to directlydown-convert the EM signal to a demodulated baseband signal. The processbegins at step 1414, which includes receiving an EM signal. Step 1416includes receiving an under-sampling signal having an aliasing rate.Step 1418 includes under-sampling the EM signal at the aliasing rate todirectly down-convert the EM signal to a baseband information signal.

This embodiment is illustrated generally by 4510 in FIG. 45B and isdescribed in Section II.2

-   -   -   2.2.3 Modulation Conversion

In another embodiment, a frequency modulated (FM) carrier signal F_(FMC)is converted to a non-FM signal F_((NON-FM)), by under-sampling the FMcarrier signal F_(FMC).F_(FMC)→F_((NON-FM))

FIG. 14D depicts a flowchart 1419 that illustrates a method forunder-sampling an FM signal to convert it to a non-FM signal. Theprocess begins at step 1420, which includes receiving the FM signal.Step 1422 includes receiving an under-sampling signal having an aliasingrate. Step 1424 includes under-sampling the FM signal at the aliasingrate to convert the FM signal to a non-FM signal. For example, the FMsignal can be under-sampled to convert it to a PM signal or an AMsignal.

This embodiment is illustrated generally by 4512 in FIG. 45B, anddescribed in Section II.3

-   -   2.3 Down-Converting by Transferring Energy

The term aliasing, as used herein, refers both to down-converting an EMsignal by under-sampling the EM signal at an aliasing rate and todown-converting an EM signal by transferring non-negligible amountsenergy from the EM signal at the aliasing rate. Methods for transferringenergy from an EM signal to down-convert the EM signal are now describedat an overview level. More detailed descriptions are provided in SectionIII.

FIG. 46A depicts a flowchart 4601 that illustrates a method fortransferring energy from the EM signal at an aliasing rate todown-convert the EM signal. The process begins at step 4602, whichincludes receiving an EM signal. Step 4604 includes receiving an energytransfer signal having an aliasing rate. Step 4606 includes transferringenergy from the EM signal at the aliasing rate to down-convert the EMsignal.

Down-converting by transferring energy is illustrated by 4506 in FIG.45A and is described in greater detail in Section III.

-   -   -   2.3.1 Down-Converting to an Intermediate Frequency (IF)            Signal

In an embodiment, EM signal is down-converted to a lower, orintermediate frequency (IF) signal, by transferring energy from the EMsignal at an aliasing rate. The EM signal can be a modulated carriersignal or an unmodulated carrier signal. In an exemplary example, amodulated carrier signal F_(MC) is down-converted to an IF signalF_(IF).F_(MC)→F_(IF)

FIG. 46B depicts a flowchart 4607 that illustrates a method fortransferring energy from the EM signal at an aliasing rate todown-convert the EM signal to an IF signal. The process begins at step4608, which includes receiving an EM signal. Step 4610 includesreceiving an energy transfer signal having an aliasing rate. Step 4612includes transferring energy from the EM signal at the aliasing rate todown-convert the EM signal to an IF signal.

This embodiment is illustrated generally by 4514 in FIG. 45B and isdescribed in Section III.1.

-   -   -   2.3.2 Direct-to-Data Down-Converting

In another embodiment, an EM signal is down-converted to a demodulatedbaseband signal by transferring energy from the EM signal at an aliasingrate. This embodiment is referred to herein as direct-to-datadown-conversion. The EM signal can be a modulated EM signal or anunmodulated EM signal. In an exemplary embodiment, the EM signal is themodulated carrier signal F_(MC), and is directly down-converted to ademodulated baseband signal F_(DMB).F_(MC)→F_(DMB)

FIG. 46C depicts a flowchart 4613 that illustrates a method fortransferring energy from the EM signal at an aliasing rate to directlydown-convert the EM signal to a demodulated baseband signal. The processbegins at step 4614, which includes receiving an EM signal. Step 4616includes receiving an energy transfer signal having an aliasing rate.Step 4618 includes transferring energy from the EM signal at thealiasing rate to directly down-convert the EM signal to a basebandsignal.

This embodiment is illustrated generally by 4516 in FIG. 45B and isdescribed in Section III.2

-   -   -   2.3.3 Modulation Conversion

In another embodiment, a frequency modulated (FM) carrier signal F_(FMC)is converted to a non-FM signal F_((NON-FM)), by transferring energyfrom the FM carrier signal F_(FMC) at an aliasing rate.F_(FMC)→F_((NON-FM))

The FM carrier signal F_(FMC) can be converted to, for example, a phasemodulated (PM) signal or an amplitude modulated (AM) signal. FIG. 46Ddepicts a flowchart 4619 that illustrates a method for transferringenergy from an FM signal to convert it to a non-FM signal. Step 4620includes receiving the FM signal. Step 4622 includes receiving an energytransfer signal having an aliasing rate. In FIG. 46D, step 4612 includestransferring energy from the FM signal to convert it to a non-FM signal.For example, energy can be transferred from an FSK signal to convert itto a PSK signal or an ASK signal.

This embodiment is illustrated generally by 4518 in FIG. 45B, anddescribed in Section III.3

-   -   2.4 Determining the Aliasing Rate

In accordance with the definition of aliasing, the aliasing rate isequal to, or less than, twice the frequency of the EM carrier signal.Preferably, the aliasing rate is much less than the frequency of thecarrier signal. The aliasing rate is preferably more than twice thehighest frequency component of the modulating baseband signal F_(MB)that is to be reproduced. The above requirements are illustrated in EQ.(1).2·F _(MC) ≧F _(AR)>2·(Highest Freq.Component of F _(MB))  EQ. (1)

In other words, by taking a carrier and aliasing it at an aliasing rate,the invention can down-convert that carrier to lower frequencies. Oneaspect that can be exploited by this invention is that the carrier isnot the item of interest; instead the lower baseband signal is ofinterest to be reproduced sufficiently. The baseband signal's frequencycontent, even though its carrier may be aliased, satisfies the Nyquistcriteria and as a result, the baseband information can be sufficientlyreproduced, either as the intermediate modulating carrier signal F_(IF)or as the demodulated direct-to-data baseband signal F_(DMB).

In accordance with the invention, relationships between the frequency ofan EM carrier signal, the aliasing rate, and the intermediate frequencyof the down-converted signal, are illustrated in EQ. (2).F _(C) =n·F _(AR) ±F _(IF)  EQ. (2)Where:

F_(C) is the frequency of the EM carrier signal that is to be aliased;

F_(AR) is the aliasing rate;

n identifies a harmonic or sub-harmonic of the aliasing rate (generally,n=0.5, 1, 2, 3, 4, . . . ); and

F_(IF) is the intermediate frequency of the down-converted signal.

Note that as (n·F_(AR)) approaches F_(C), F_(IF) approaches zero. Thisis a special case where an EM signal is directly down-converted to ademodulated baseband signal. This special case is referred to herein asDirect-to-Data down-conversion. Direct-to-Data down-conversion isdescribed in later sections.

High level descriptions, exemplary embodiments and exemplaryimplementations of the above and other embodiments of the invention areprovided in sections below.

3. Benefits of the Invention Using an Example Conventional Receiver forComparison

FIG. 11 illustrates an example conventional receiver system 1102. Theconventional system 1102 is provided both to help the reader tounderstand the functional differences between conventional systems andthe present invention, and to help the reader to understand the benefitsof the present invention.

The example conventional receiver system 1102 receives anelectromagnetic (EM) signal 1104 via an antenna 1106. The EM signal 1104can include a plurality of EM signals such as modulated carrier signals.For example, the EM signal 1104 includes one or more radio frequency(RF) EM signals, such as a 900 MHZ modulated carrier signal. Higherfrequency RF signals, such as 900 MHZ signals, generally cannot bedirectly processed by conventional signal processors. Instead, higherfrequency RF signals are typically down-converted to lower intermediatefrequencies (IF) for processing. The receiver system 1102 down-convertsthe EM signal 1104 to an intermediate frequency (IF) signal 1108 n,which can be provided to a signal processor 1110. When the EM signal1104 includes a modulated carrier signal, the signal processor 1110usually includes a demodulator that demodulates the IF signal 1108 n toa baseband information signal (demodulated baseband signal).

Receiver system 1102 includes an RF stage 1112 and one or more IF stages1114. The RF stage 1112 receives the EM signal 1104. The RF stage 1112includes the antenna 1106 that receives the EM signal 1104.

The one or more IF stages 1114 a–1114 n down-convert the EM signal 1104to consecutively lower intermediate frequencies. Each of the one or moreIF sections 1114 a–1114 n includes a mixer 1118 a–1118 n thatdown-converts an input EM signal 1116 to a lower frequency IF signal1108. By cascading the one or more mixers 1118 a–1118 n, the EM signal1104 is incrementally down-converted to a desired IF signal 1108 n.

In operation, each of the one or more mixers 1118 mixes an input EMsignal 1116 with a local oscillator (LO) signal 1119, which is generatedby a local oscillator (LO) 1120. Mixing generates sum and differencesignals from the input EM signal 1116 and the LO signal 1119. Forexample, mixing an input EM signal 1116 a, having a frequency of 900MHZ, with a LO signal 1119 a, having a frequency of 830 MHZ, results ina sum signal, having a frequency of 900 MHZ+830 MHZ=1.73 GHZ, and adifference signal, having a frequency of 900 MHZ−830 MHZ=70 MHZ.

Specifically, in the example of FIG. 11, the one or more mixers 1118generate a sum and difference signals for all signal components in theinput EM signal 1116. For example, when the EM signal 1116 a includes asecond EM signal, having a frequency of 760 MHZ, the mixer 1118 agenerates a second sum signal, having a frequency of 760 MHZ+830MHZ=1.59 GHZ, and a second difference signal, having a frequency of 830MHZ−760 MHZ=70 MHZ. In this example, therefore, mixing two input EMsignals, having frequencies of 900 MHZ and 760 MHZ, respectively, withan LO signal having a frequency of 830 MHZ, results in two IF signals at70 MHZ.

Generally, it is very difficult, if not impossible, to separate the two70 MHZ signals. Instead, one or more filters 1122 and 1123 are providedupstream from each mixer 1118 to filter the unwanted frequencies, alsoknown as image frequencies. The filters 1122 and 1123 can includevarious filter topologies and arrangements such as bandpass filters, oneor more high pass filters, one or more low pass filters, combinationsthereof, etc.

Typically, the one or more mixers 1118 and the one or more filters 1122and 1123 attenuate or reduce the strength of the EM signal 1104. Forexample, a typical mixer reduces the EM signal strength by 8 to 12 dB. Atypical filter reduces the EM signal strength by 3 to 6 dB.

As a result, one or more low noise amplifiers (LNAs) 1121 and 1124a–1124 n are provided upstream of the one or more filters 1123 and 1122a–1122 n. The LNAs and filters can be in reversed order. The LNAscompensate for losses in the mixers 1118, the filters 1122 and 1123, andother components by increasing the EM signal strength prior to filteringand mixing. Typically, for example, each LNA contributes 15 to 20 dB ofamplification.

However, LNAs require substantial power to operate. Higher frequencyLNAs require more power than lower frequency LNAs. When the receiversystem 1102 is intended to be portable, such as a cellular telephonereceiver, for example, the LNAs require a substantial portion of thetotal power.

At higher frequencies, impedance mismatches between the various stagesfurther reduce the strength of the EM signal 1104. In order to optimizepower transferred through the receiver system 1102, each componentshould be impedance matched with adjacent components. Since no twocomponents have the exact same impedance characteristics, even forcomponents that were manufactured with high tolerances, impedancematching must often be individually fine tuned for each receiver system1102. As a result, impedance matching in conventional receivers tends tobe labor intensive and more art than science. Impedance matchingrequires a significant amount of added time and expense to both thedesign and manufacture of conventional receivers. Since many of thecomponents, such as LNA, filters, and impedance matching circuits, arehighly frequency dependent, a receiver designed for one application isgenerally not suitable for other applications. Instead, a new receivermust be designed, which requires new impedance matching circuits betweenmany of the components.

Conventional receiver components are typically positioned over multipleIC substrates instead of on a single IC substrate. This is partlybecause there is no single substrate that is optimal for both RF, IF,and baseband frequencies. Other factors may include the sheer number ofcomponents, their various sizes and different inherent impedancecharacteristics, etc. Additional signal amplification is often requiredwhen going from chip to chip. Implementation over multiple substratesthus involves many costs in addition to the cost of the ICs themselves.

Conventional receivers thus require many components, are difficult andtime consuming to design and manufacture, and require substantialexternal power to maintain sufficient signal levels. Conventionalreceivers are thus expensive to design, build, and use.

In an embodiment, the present invention is implemented to replace many,if not all, of the components between the antenna 1106 and the signalprocessor 1110, with an aliasing module that includes a universalfrequency translator (UFT) module. The UFT is able to down-convert awide range of EM signal frequencies using very few components. The UFTis easy to design and build, and requires very little external power.The UFT design can be easily tailored for different frequencies orfrequency ranges. For example, UFT design can be easily impedancematched with relatively little tuning. In a direct-to-data embodiment ofthe invention, where an EM signal is directly down-converted to ademodulated baseband signal, the invention also eliminates the need fora demodulator in the signal processor 1110.

When the invention is implemented in a receiver system, such as thereceiver system 1102, power consumption is significantly reduced andsignal to noise ratio is significantly increased.

In an embodiment, the invention can be implemented and tailored forspecific applications with easy to calculate and easy to implementimpedance matching circuits. As a result, when the invention isimplemented as a receiver, such as the receiver 1102, specializedimpedance matching experience is not required.

In conventional receivers, components in the IF sections compriseroughly eighty to ninety percent of the total components of thereceivers. The UFT design eliminates the IF section(s) and thuseliminates the roughly eighty to ninety percent of the total componentsof conventional receivers.

Other advantages of the invention include, but are not limited to:

The invention can be implemented as a receiver with only a single localoscillator;

The invention can be implemented as a receiver with only a single, lowerfrequency, local oscillator;

The invention can be implemented as a receiver using few filters;

The invention can be implemented as a receiver using unit delay filters;

The invention can be implemented as a receiver that can changefrequencies and receive different modulation formats with no hardwarechanges;

The invention can be also be implemented as frequency up-converter in anEM signal transmitter;

The invention can be also be implemented as a combination up-converter(transmitter) and down-converter (receiver), referred to herein as atransceiver;

The invention can be implemented as a method and system for ensuringreception of a communications signal, as disclosed in co-pending patentapplication titled, “Method and System for Ensuring Reception of aCommunications Signal,” Ser. No. 09/176,415, filed Oct. 21, 1998, (U.S.Pat. No. 6,061,555), incorporated herein by reference in its entirety;

The invention can be implemented in a differential configuration,whereby signal to noise ratios are increased;

A receiver designed in accordance with the invention can be implementedon a single IC substrate, such as a silicon-based IC substrate;

A receiver designed in accordance with the invention and implemented ona single IC substrate, such as a silicon-based IC substrate, candown-convert EM signals from frequencies in the giga Hertz range;

A receiver built in accordance with the invention has a relatively flatresponse over a wide range of frequencies. For example, in anembodiment, a receiver built in accordance with the invention to operatearound 800 MHZ has a substantially flat response (i.e., plus or minus afew dB of power) from 100 MHZ to 1 GHZ. This is referred to herein as awide-band receiver; and

A receiver built in accordance with the invention can include multiple,user-selectable, Impedance match modules, each designed for a differentwide-band of frequencies, which can be used to scan an ultra-wide-bandof frequencies.

II. Down-Converting by Under-Sampling

1. Down-Converting an EM Carrier Signal to an EM Intermediate Signal byUnder-Sampling the EM Carrier Signal at the Aliasing Rate

In an embodiment, the invention down-converts an EM signal to an IFsignal by under-sampling the EM signal. This embodiment is illustratedby 4508 in FIG. 45B.

This embodiment can be implemented with modulated and unmodulated EMsignals. This embodiment is described herein using the modulated carriersignal F_(MC) in FIG. 1, as an example. In the example, the modulatedcarrier signal F_(MC) is down-converted to an IF signal F_(IF). The IFsignal F_(IF) can then be demodulated, with any conventionaldemodulation technique to obtain a demodulated baseband signal F_(DMB).Upon reading the disclosure and examples therein, one skilled in therelevant art(s) will understand that the invention can be implemented todown-convert any EM signal, including but not limited to, modulatedcarrier signals and unmodulated carrier signals.

The following sections describe example methods for down-converting themodulated carrier signal F_(MC) to the IF signal F_(IF), according toembodiments of the invention. Exemplary structural embodiments forimplementing the methods are also described. It should be understoodthat the invention is not limited to the particular embodimentsdescribed below. Equivalents, extensions, variations, deviations, etc.,of the following will be apparent to persons skilled in the relevantart(s) based on the teachings contained herein. Such equivalents,extensions, variations, deviations, etc., are within the scope andspirit of the present invention.

The following sections include a high level discussion, exampleembodiments, and implementation examples.

-   -   1.1 High Level Description

This section (including its subsections) provides a high-leveldescription of down-converting an EM signal to an IF signal F_(IF),according to the invention. In particular, an operational process ofunder-sampling a modulated carrier signal F_(MC) to down-convert it tothe IF signal F_(IF), is described at a high-level. Also, a structuralimplementation for implementing this process is described at ahigh-level. This structural implementation is described herein forillustrative purposes, and is not limiting. In particular, the processdescribed in this section can be achieved using any number of structuralimplementations, one of which is described in this section. The detailsof such structural implementations will be apparent to persons skilledin the relevant art(s) based on the teachings contained herein.

-   -   -   1.1.1 Operational Description

FIG. 14B depicts a flowchart 1407 that illustrates an exemplary methodfor under-sampling an EM signal to down-convert the EM signal to anintermediate signal F_(IF). The exemplary method illustrated in theflowchart 1407 is an embodiment of the flowchart 1401 in FIG. 14A.

Any and all combinations of modulation techniques are valid for thisinvention. For ease of discussion, the digital AM carrier signal 616 isused to illustrate a high level operational description of theinvention. Subsequent sections provide detailed flowcharts anddescriptions for AM, FM and PM example embodiments. Upon reading thedisclosure and examples therein, one skilled in the relevant art(s) willunderstand that the invention can be implemented to down-convert anytype of EM signal, including any form of modulated carrier signal andunmodulated carrier signals.

The method illustrated in the flowchart 1407 is now described at a highlevel using the digital AM carrier signal 616 of FIG. 6C. The digital AMcarrier signal 616 is re-illustrated in FIG. 15A for convenience. FIG.15E illustrates a portion 1510 of the AM carrier signal 616, betweentime t1 and t2, on an expanded time scale.

The process begins at step 1408, which includes receiving an EM signal.Step 1408 is represented by the digital AM carrier signal 616.

Step 1410 includes receiving an under-sampling signal having an aliasingrate F_(AR). FIG. 15B illustrates an example under-sampling signal 1502,which includes a train of pulses 1504 having negligible apertures thattend toward zero time in duration. The pulses 1504 repeat at thealiasing rate, or pulse repetition rate. Aliasing rates are discussedbelow.

Step 1412 includes under-sampling the EM signal at the aliasing rate todown-convert the EM signal to the intermediate signal F_(IF). Whendown-converting an EM signal to an IF signal, the frequency or aliasingrate of the pulses 1504 sets the IF.

FIG. 15C illustrates a stair step AM intermediate signal 1506, which isgenerated by the down-conversion process. The AM intermediate signal1506 is similar to the AM carrier signal 616 except that the AMintermediate signal 1506 has a lower frequency than the AM carriersignal 616. The AM carrier signal 616 has thus been down-converted tothe AM intermediate signal 1506. The AM intermediate signal 1506 can begenerated at any frequency below the frequency of the AM carrier signal616 by adjusting the aliasing rate.

FIG. 15D depicts the AM intermediate signal 1506 as a filtered outputsignal 1508. In an alternative embodiment, the invention outputs a stairstep, non-filtered or partially filtered output signal. The choicebetween filtered, partially filtered and non-filtered output signals isgenerally a design choice that depends upon the application of theinvention.

The intermediate frequency of the down-converted signal F_(IF), which inthis example is the AM intermediate signal 1506, can be determined fromEQ. (2), which is reproduced below for convenience.F _(C) =n·F _(AR) ±F _(IF)  EQ. (2)

A suitable aliasing rate F_(AR) can be determined in a variety of ways.An example method for determining the aliasing rate F_(AR), is providedbelow. After reading the description herein, one skilled in the relevantart(s) will understand how to determine appropriate aliasing rates forEM signals, including ones in addition to the modulated carrier signalsspecifically illustrated herein.

In FIG. 17, a flowchart 1701 illustrates an example process fordetermining an aliasing rate F_(AR). But a designer may choose, or anapplication may dictate, that the values be determined in an order thatis different than the illustrated order. The process begins at step1702, which includes determining, or selecting, the frequency of the EMsignal. The frequency of the FM carrier signal 616 can be, for example,901 MHZ.

Step 1704 includes determining, or selecting, the intermediatefrequency. This is the frequency to which the EM signal will bedown-converted. The intermediate frequency can be determined, orselected, to match a frequency requirement of a down-stream demodulator.The intermediate frequency can be, for example, 1 MHZ.

Step 1706 includes determining the aliasing rate or rates that willdown-convert the EM signal to the IF specified in step 1704.

EQ. (2) can be rewritten as EQ. (3):n·Far=F _(C) ±F _(IF)  EQ. (3)

Which can be rewritten as EQ. (4):

$\begin{matrix}{n = \frac{F_{C} \pm F_{IF}}{F_{AR}}} & {{EQ}.\mspace{20mu}(4)}\end{matrix}$

or as EQ. (5):

$\begin{matrix}{F_{AR} = \frac{F_{C} \pm F_{IF}}{n}} & {{EQ}.\mspace{20mu}(5)}\end{matrix}$

(F_(C)±F_(IF)) can be defined as a difference value F_(DIFF), asillustrated in EQ. (6):(F _(C) ±F _(IF))=F _(DIFF)  EQ. (6)

EQ. (4) can be rewritten as EQ. (7):

$\begin{matrix}{n = \frac{F_{DIFF}}{F_{AR}}} & {{EQ}.\mspace{20mu}(7)}\end{matrix}$

From EQ. (7), it can be seen that, for a given n and a constant F_(AR),F_(DIFF) is constant. For the case of F_(DIFF)=F_(C)−F_(IF), and for aconstant F_(DIFF), as F_(C) increases, F_(IF) necessarily increases. Forthe case of F_(DIFF)=F_(C)+F_(IF), and for a constant F_(DIFF), as F_(C)increases, F_(IF) necessarily decreases. In the latter case ofF_(DIFF)=F_(C)+F_(IF), any phase or frequency changes on F_(C)correspond to reversed or inverted phase or frequency changes on F_(IF).This is mentioned to teach the reader that if F_(DIFF)=F_(C)+F_(IF) isused, the above effect will affect the phase and frequency response ofthe modulated intermediate signal F_(IF).

EQs. (2) through (7) can be solved for any valid n. A suitable n can bedetermined for any given difference frequency F_(DIFF) and for anydesired aliasing rate F_(AR(Desired)). EQs. (2) through (7) can beutilized to identify a specific harmonic closest to a desired aliasingrate F_(AR(Desired)) that will generate the desired intermediate signalF_(IF).

An example is now provided for determining a suitable n for a givendifference frequency F_(DIFF) and for a desired aliasing rateF_(AR(Desired)). For ease of illustration, only the case of(F_(C)−F_(IF)) is illustrated in the example below.

$n = {\frac{F_{C} - F_{IF}}{F_{{AR}_{({Desired})}}} = \frac{F_{DIFF}}{F_{{AR}_{({Desired})}}}}$

The desired aliasing rate F_(AR(Desired)) can be, for example, 140 MHZ.Using the previous examples, where the carrier frequency is 901 MHZ andthe IF is 1 MHZ, an initial value of n is determined as:

$n = {\frac{{901\mspace{14mu}{MHZ}} - {1\mspace{14mu}{MHZ}}}{140\mspace{14mu}{MHZ}} = {\frac{900}{140} = 6.4}}$

The initial value 6.4 can be rounded up or down to the valid nearest n,which was defined above as including (0.5, 1, 2, 3, . . . ). In thisexample, 6.4 is rounded down to 6.0, which is inserted into EQ. (5) forthe case of (F_(C)−F_(IF))=F_(DIFF).:

$F_{AR} = \frac{F_{C} - F_{IF}}{n}$$F_{AR} = {\frac{{901\mspace{14mu}{MHZ}} - {1\mspace{14mu}{MHZ}}}{6} = {\frac{900\mspace{14mu}{MHZ}}{6} = {150\mspace{14mu}{MHZ}}}}$

In other words, under-sampling a 901 MHZ EM carrier signal at 150 MHZgenerates an intermediate signal at 1 MHZ. When the under-sampled EMcarrier signal is a modulated carrier signal, the intermediate signalwill also substantially include the modulation. The modulatedintermediate signal can be demodulated through any conventionaldemodulation technique.

Alternatively, instead of starting from a desired aliasing rate, a listof suitable aliasing rates can be determined from the modified form ofEQ. (5), by solving for various values of n. Example solutions arelisted below.

$F_{AR} = {\frac{\left( {F_{C} - F_{IF}} \right)}{n} = {\frac{F_{DIFF}}{n} = {\frac{{901\mspace{14mu}{MHZ}} - {1\mspace{14mu}{MHZ}}}{n} = \frac{900\mspace{14mu}{MHZ}}{n}}}}$

Solving for n=0.5, 1, 2, 3, 4, 5 and 6:

900 MHZ/0.5=1.8 GHZ (i.e., second harmonic, illustrated in FIG. 25A as2502);

900 MHZ/1=900 MHZ (i.e., fundamental frequency, illustrated in FIG. 25Bas 2504);

900 MHZ/2=450 MHZ (i.e., second sub-harmonic, illustrated in FIG. 25C as2506);

900 MHZ/3=300 MHZ (i.e., third sub-harmonic, illustrated in FIG. 25D as2508);

900 MHZ/4=225 MHZ (i.e., fourth sub-harmonic, illustrated in FIG. 25E as2510);

900 MHZ/5=180 MHZ(i.e., fifth sub-harmonic, illustrated in FIG. 25F as2512); and

900 MHZ/6=150 MHZ(i.e., sixth sub-harmonic, illustrated in FIG. 25G as2514).

The steps described above can be performed for the case of(F_(C)+F_(IF)) in a similar fashion. The results can be compared to theresults obtained from the case of (F_(C)−F_(IF)) to determine whichprovides better result for an application.

In an embodiment, the invention down-converts an EM signal to arelatively standard IF in the range of, for example, 100 KHZ to 200 MHZ.In another embodiment, referred to herein as a small off-setimplementation, the invention down-converts an EM signal to a relativelylow frequency of, for example, less than 100 KHZ. In another embodiment,referred to herein as a large off-set implementation, the inventiondown-converts an EM signal to a relatively higher IF signal, such as,for example, above 200 MHZ.

The various off-set implementations provide selectivity for differentapplications. Generally, lower data rate applications can operate atlower intermediate frequencies. But higher intermediate frequencies canallow more information to be supported for a given modulation technique.

In accordance with the invention, a designer picks an optimuminformation bandwidth for an application and an optimum intermediatefrequency to support the baseband signal. The intermediate frequencyshould be high enough to support the bandwidth of the modulatingbaseband signal F_(MB).

Generally, as the aliasing rate approaches a harmonic or sub-harmonicfrequency of the EM signal, the frequency of the down-converted IFsignal decreases. Similarly, as the aliasing rate moves away from aharmonic or sub-harmonic frequency of the EM signal, the IF increases.

Aliased frequencies occur above and below every harmonic of the aliasingfrequency. In order to avoid mapping other aliasing frequencies in theband of the aliasing frequency (IF) of interest, the IF of interest ispreferably not near one half the aliasing rate.

As described in example implementations below, an aliasing module,including a universal frequency translator (UFT) module built inaccordance with the invention, provides a wide range of flexibility infrequency selection and can thus be implemented in a wide range ofapplications. Conventional systems cannot easily offer, or do not allow,this level of flexibility in frequency selection.

-   -   -   1.1.2 Structural Description

FIG. 16 illustrates a block diagram of an under-sampling system 1602according to an embodiment of the invention. The under-sampling system1602 is an example embodiment of the generic aliasing system 1302 inFIG. 13. The under-sampling system 1602 includes an under-samplingmodule 1606. The under-sampling module 1606 receives the EM signal 1304and an under-sampling signal 1604, which includes under-sampling pulseshaving negligible apertures that tend towards zero time, occurring at afrequency equal to the aliasing rate F_(AR). The under-sampling signal1604 is an example embodiment of the aliasing signal 1310. Theunder-sampling module 1606 under-samples the EM signal 1304 at thealiasing rate F_(AR) of the under-sampling signal 1604. Theunder-sampling system 1602 outputs a down-converted signal 1308A.

Preferably, the under-sampling module 1606 under-samples the EM signal1304 to down-convert it to the intermediate signal F_(IF) in the mannershown in the operational flowchart 1407 of FIG. 14B. But it should beunderstood that the scope and spirit of the invention includes otherstructural embodiments for performing the steps of the flowchart 1407.The specifics of the other structural embodiments will be apparent topersons skilled in the relevant art(s) based on the discussion containedherein. In an embodiment, the aliasing rate F_(AR) of the under-samplingsignal 1604 is chosen in the manner discussed in Section II.1.1.1 sothat the under-sampling module 1606 under-samples the EM carrier signal1304 generating the intermediate frequency F_(IF).

The operation of the under-sampling system 1602 is now described withreference to the flowchart 1407 and to the timing diagrams in FIGS.15A–D. In step 1408, the under-sampling module 1606 receives the AMsignal 616 (FIG. 15A). In step 1410, the under-sampling module 1606receives the under-sampling signal 1502 (FIG. 15B). In step 1412, theunder-sampling module 1606 under-samples the AM carrier signal 616 atthe aliasing rate of the under-sampling signal 1502, or a multiplethereof, to down-convert the AM carrier signal 616 to the intermediatesignal 1506 (FIG. 15D).

Example implementations of the under-sampling module 1606 are providedin Sections 4 and 5 below.

-   -   1.1 Example Embodiments

Various embodiments related to the method(s) and structure(s) describedabove are presented in this section (and its subsections). Theseembodiments are described herein for purposes of illustration, and notlimitation. The invention is not limited to these embodiments. Alternateembodiments (including equivalents, extensions, variations, deviations,etc., of the embodiments described herein) will be apparent to personsskilled in the relevant art(s) based on the teachings contained herein.The invention is intended and adapted to include such alternateembodiments.

The method for down-converting the EM signal 1304 to the intermediatesignal F_(IF), illustrated in the flowchart 1407 of FIG. 14B, can beimplemented with any type of EM signal, including unmodulated EM carriersignals and modulated carrier signals including, but not limited to, AM,FM, PM, etc., or any combination thereof. Operation of the flowchart1407 of FIG. 14B is described below for AM, FM and PM carrier signals.The exemplary descriptions below are intended to facilitate anunderstanding of the present invention. The present invention is notlimited to or by the exemplary embodiments below.

-   -   -   1.2.1 First Example Embodiment: Amplitude Modulation            -   1.2.1.1 Operational Description

Operation of the exemplary process of the flowchart 1407 in FIG. 14B isdescribed below for the analog AM carrier signal 516, illustrated inFIG. 5C, and for the digital AM carrier signal 616, illustrated in FIG.6C.

-   -   -   -   -   1.2.1.1.1 Analog AM Carrier Signal

A process for down-converting the analog AM carrier signal 516 in FIG.5C to an analog AM intermediate signal is now described with referenceto the flowchart 1407 in FIG. 14B. The analog AM carrier signal 516 isre-illustrated in FIG. 19A for convenience. For this example, the analogAM carrier signal 516 oscillates at approximately 901 MHZ. In FIG. 19B,an analog AM carrier signal 1904 illustrates a portion of the analog AMcarrier signal 516 on an expanded time scale.

The process begins at step 1408, which includes receiving the EM signal.This is represented by the analog AM carrier signal 516 in FIG. 19A.

Step 1410 includes receiving an under-sampling signal having an aliasingrate F_(AR). FIG. 19C illustrates an example under-sampling signal 1906on approximately the same time scale as FIG. 19B. The under-samplingsignal 1906 includes a train of pulses 1907 having negligible aperturesthat tend towards zero time in duration. The pulses 1907 repeat at thealiasing rate, or pulse repetition rate, which is determined or selectedas previously described. Generally, when down-converting to anintermediate signal, the aliasing rate F_(AR) is substantially equal toa harmonic or, more typically, a sub-harmonic of the differencefrequency F_(DIFF). For this example, the aliasing rate is approximately450 MHZ.

Step 1412 includes under-sampling the EM signal at the aliasing rate todown-convert the EM signal to the intermediate signal F_(IF). Step 1412is illustrated in FIG. 19B by under-sample points 1905.

Because a harmonic of the aliasing rate is off-set from the AM carriersignal 516, the under-sample points 1905 “walk through” the analog AMcarrier signal 516. In this example, the under-sample points 1905 “walkthrough” the analog AM carrier signal 516 at approximately a onemegahertz rate. In other words, the under-sample points 1905 occur atdifferent locations on subsequent cycles of the AM carrier signal 516.As a result, the under-sample points 1905 capture varying amplitudes ofthe analog AM signal 516. For example, under-sample point 1905A has alarger amplitude than under-sample point 1905B.

In FIG. 19D, the under-sample points 1905 correlate to voltage points1908. In an embodiment, the voltage points 1908 form an analog AMintermediate signal 1910. This can be accomplished in many ways. Forexample, each voltage point 1908 can be held at a relatively constantlevel until the next voltage point is received. This results in astair-step output which can be smoothed or filtered if desired, asdiscussed below.

In FIG. 19E, an AM intermediate signal 1912 represents the AMintermediate signal 1910, after filtering, on a compressed time scale.Although FIG. 19E illustrates the AM intermediate signal 1912 as afiltered output signal, the output signal does not need to be filteredor smoothed to be within the scope of the invention. Instead, the outputsignal can be tailored for different applications.

The AM intermediate signal 1912 is substantially similar to the AMcarrier signal 516, except that the AM intermediate signal 1912 is atthe 1 MHZ intermediate frequency. The AM intermediate signal 1912 can bedemodulated through any conventional AM demodulation technique.

The drawings referred to herein illustrate frequency down-conversion inaccordance with the invention. For example, the AM intermediate signal1910 in FIG. 19D and the AM intermediate signal 1912 in FIG. 19Eillustrate that the AM carrier signal 516 was successfullydown-converted to an intermediate signal by retaining enough basebandinformation for sufficient reconstruction.

-   -   -   -   -   1.2.1.1.2 Digital AM Carrier Signal

A process for down-converting the digital AM carrier signal 616 in FIG.6C to a digital AM intermediate signal is now described with referenceto the flowchart 1407 in FIG. 14B. The digital AM carrier signal 616 isre-illustrated in FIG. 18A for convenience. For this example, thedigital AM carrier signal 616 oscillates at approximately 901 MHZ. InFIG. 18B, an AM carrier signal 1804 illustrates a portion of the AMsignal 616, from time t0 to t1, on an expanded time scale.

The process begins at step 1408, which includes receiving an EM signal.This is represented by the AM signal 616 in FIG. 18A.

Step 1410 includes receiving an under-sampling signal having an aliasingrate F_(AR). FIG. 18C illustrates an example under-sampling signal 1806on approximately the same time scale as FIG. 18B. The under-samplingsignal 1806 includes a train of pulses 1807 having negligible aperturesthat tend towards zero time in duration. The pulses 1807 repeat at thealiasing rate, or pulse repetition rate, which is determined or selectedas previously described. Generally, when down-converting to anintermediate signal, the aliasing rate F_(AR) is substantially equal toa harmonic or, more typically, a sub-harmonic of the differencefrequency F_(DIFF). For this example, the aliasing rate is approximately450 MHZ.

Step 1412 includes under-sampling the EM signal at the aliasing rate todown-convert the EM signal to the intermediate signal F_(IF). Step 1412is illustrated in FIG. 18B by under-sample points 1805.

Because a harmonic of the aliasing rate is off-set from the AM carriersignal 616, the under-sample points 1805 walk through the AM carriersignal 616. In other words, the under-sample points 1805 occur atdifferent locations of subsequent cycles of the AM signal 616. As aresult, the under-sample points 1805 capture various amplitudes of theAM signal 616. In this example, the under-sample points 1805 walkthrough the AM carrier signal 616 at approximately a 1 MHZ rate. Forexample, under-sample point 1805A has a larger amplitude thanunder-sample point 1805B.

In FIG. 18D, the under-sample points 1805 correlate to voltage points1808. In an embodiment, the voltage points 1805 form an AM intermediatesignal 1810. This can be accomplished in many ways. For example, eachvoltage point 1808 can be held at a relatively constant level until thenext voltage point is received. This results in a stair-step outputwhich can be smoothed or filtered if desired, as discussed below.

In FIG. 18E, an AM intermediate signal 1812 represents the AMintermediate signal 1810, after filtering, on a compressed time scale.Although FIG. 18E illustrates the AM intermediate signal 1812 as afiltered output signal, the output signal does not need to be filteredor smoothed to be within the scope of the invention. Instead, the outputsignal can be tailored for different applications.

The AM intermediate signal 1812 is substantially similar to the AMcarrier signal 616, except that the AM intermediate signal 1812 is atthe 1 MHZ intermediate frequency. The AM intermediate signal 1812 can bedemodulated through any conventional AM demodulation technique.

The drawings referred to herein illustrate frequency down-conversion inaccordance with the invention. For example, the AM intermediate signal1810 in FIG. 18D and the AM intermediate signal 1812 in FIG. 18Eillustrate that the AM carrier signal 616 was successfullydown-converted to an intermediate signal by retaining enough basebandinformation for sufficient reconstruction.

-   -   -   -   1.2.1.2 Structural Description

The operation of the under-sampling system 1602 is now described for theanalog AM carrier signal 516, with reference to the flowchart 1407 andto the timing diagrams of FIGS. 19A–E. In step 1408, the under-samplingmodule 1606 receives the AM carrier signal 516 (FIG. 19A). In step 1410,the under-sampling module 1606 receives the under-sampling signal 1906(FIG. 19C). In step 1412, the under-sampling module 1606 under-samplesthe AM carrier signal 516 at the aliasing rate of the under-samplingsignal 1906 to down-convert it to the AM intermediate signal 1912 (FIG.19E).

The operation of the under-sampling system 1602 is now described for thedigital AM carrier signal 616, with reference to the flowchart 1407 andto the timing diagrams of FIGS. 18A–E. In step 1408, the under-samplingmodule 1606 receives the AM carrier signal 616 (FIG. 18A). In step 1410,the under-sampling module 1606 receives the under-sampling signal 1806(FIG. 18C). In step 1412, the under-sampling module 1606 under-samplesthe AM carrier signal 616 at the aliasing rate of the under-samplingsignal 1806 to down-convert it to the AM intermediate signal 1812 (FIG.18E).

Example implementations of the under-sampling module 1606 are providedin Sections 4 and 5 below.

-   -   -   1.2.2 Second Example Embodiment: Frequency Modulation            -   1.2.2.1 Operational Description

Operation of the exemplary process of the flowchart 1407 in FIG. 14B isdescribed below for the analog FM carrier signal 716, illustrated inFIG. 7C, and for the digital FM carrier signal 816, illustrated in FIG.8C.

-   -   -   -   -   1.2.2.1.1 Analog FM Carrier Signal

A process for down-converting the analog FM carrier signal 716 to ananalog FM intermediate signal is now described with reference to theflowchart 1407 in FIG. 14B. The analog FM carrier signal 716 isre-illustrated in FIG. 20A for convenience. For this example, the analogFM carrier signal 716 oscillates at approximately 901 MHZ. In FIG. 20B,an FM carrier signal 2004 illustrates a portion of the analog FM carriersignal 716, from time t1 to t3, on an expanded time scale.

The process begins at step 1408, which includes receiving an EM signal.This is represented in FIG. 20A by the FM carrier signal 716.

Step 1410 includes receiving an under-sampling signal having an aliasingrate F_(AR). FIG. 20C illustrates an example under-sampling signal 2006on approximately the same time scale as FIG. 20B. The under-samplingsignal 2006 includes a train of pulses 2007 having negligible aperturesthat tend towards zero time in duration. The pulses 2007 repeat at thealiasing rate or pulse repetition rate, which is determined or selectedas previously described. Generally, when down-converting to anintermediate signal, the aliasing rate F_(AR) is substantially equal toa harmonic or, more typically, a sub-harmonic of the differencefrequency F_(DIFF). For this example, where the FM carrier signal 716 iscentered around 901 MHZ, the aliasing rate is approximately 450 MHZ.

Step 1412 includes under-sampling the EM signal at the aliasing rate todown-convert the EM signal to the intermediate signal F_(IF). Step 1412is illustrated in FIG. 20B by under-sample points 2005.

Because a harmonic of the aliasing rate is off-set from the FM carriersignal 716, the under-sample points 2005 occur at different locations ofsubsequent cycles of the under-sampled signal 716. In other words, theunder-sample points 2005 walk through the signal 716. As a result, theunder-sample points 2005 capture various amplitudes of the FM carriersignal 716.

In FIG. 20D, the under-sample points 2005 correlate to voltage points2008. In an embodiment, the voltage points 2005 form an analog FMintermediate signal 2010. This can be accomplished in many ways. Forexample, each voltage point 2008 can be held at a relatively constantlevel until the next voltage point is received. This results in astair-step output which can be smoothed or filtered if desired, asdiscussed below.

In FIG. 20E, an FM intermediate signal 2012 illustrates the FMintermediate signal 2010, after filtering, on a compressed time scale.Although FIG. 20E illustrates the FM intermediate signal 2012 as afiltered output signal, the output signal does not need to be filteredor smoothed to be within the scope of the invention. Instead, the outputsignal can be tailored for different applications.

The FM intermediate signal 2012 is substantially similar to the FMcarrier signal 716, except that the FM intermediate signal 2012 is atthe 1 MHZ intermediate frequency. The FM intermediate signal 2012 can bedemodulated through any conventional FM demodulation technique.

The drawings referred to herein illustrate frequency down-conversion inaccordance with the invention. For example, the FM intermediate signal2010 in FIG. 20D and the FM intermediate signal 2012 in FIG. 20Eillustrate that the FM carrier signal 716 was successfullydown-converted to an intermediate signal by retaining enough basebandinformation for sufficient reconstruction.

-   -   -   -   -   1.2.2.1.2 Digital FM Carrier Signal

A process for down-converting the digital FM carrier signal 816 to adigital FM intermediate signal is now described with reference to theflowchart 1407 in FIG. 14B. The digital FM carrier signal 816 isre-illustrated in FIG. 21A for convenience. For this example, thedigital FM carrier signal 816 oscillates at approximately 901 MHZ. InFIG. 21B, an FM carrier signal 2104 illustrates a portion of the FMcarrier signal 816, from time t1 to t3, on an expanded time scale.

The process begins at step 1408, which includes receiving an EM signal.This is represented in FIG. 21A, by the FM carrier signal 816.

Step 1410 includes receiving an under-sampling signal having an aliasingrate F_(AR). FIG. 21C illustrates an example under-sampling signal 2106on approximately the same time scale as FIG. 21B. The under-samplingsignal 2106 includes a train of pulses 2107 having negligible aperturesthat tend toward zero time in duration. The pulses 2107 repeat at thealiasing rate, or pulse repetition rate, which is determined or selectedas previously described. Generally, when down-converting to anintermediate signal, the aliasing rate F_(AR) is substantially equal toa harmonic or, more typically, a sub-harmonic of the differencefrequency F_(DIFF). In this example, where the FM carrier signal 816 iscentered around 901 MHZ, the aliasing rate is selected as approximately450 MHZ, which is a sub-harmonic of 900 MHZ, which is off-set by 1 MHZfrom the center frequency of the FM carrier signal 816.

Step 1412 includes under-sampling the EM signal at the aliasing rate todown-convert the EM signal to an intermediate signal F_(IF). Step 1412is illustrated in FIG. 21B by under-sample points 2105.

Because a harmonic of the aliasing rate is off-set from the FM carriersignal 816, the under-sample points 2105 occur at different locations ofsubsequent cycles of the FM carrier signal 816. In other words, theunder-sample points 2105 walk through the signal 816. As a result, theunder-sample points 2105 capture various amplitudes of the signal 816.

In FIG. 21D, the under-sample points 2105 correlate to voltage points2108. In an embodiment, the voltage points 2108 form a digital FMintermediate signal 2110. This can be accomplished in many ways. Forexample, each voltage point 2108 can be held at a relatively constantlevel until the next voltage point is received. This results in astair-step output which can be smoothed or filtered if desired, asdescribed below.

In FIG. 21E, an FM intermediate signal 2112 represents the FMintermediate signal 2110, after filtering, on a compressed time scale.Although FIG. 21E illustrates the FM intermediate signal 2112 as afiltered output signal, the output signal does not need to be filteredor smoothed to be within the scope of the invention. Instead, the outputsignal can be tailored for different applications.

The FM intermediate signal 2112 is substantially similar to the FMcarrier signal 816, except that the FM intermediate signal 2112 is atthe 1 MHZ intermediate frequency. The FM intermediate signal 2112 can bedemodulated through any conventional FM demodulation technique.

The drawings referred to herein illustrate frequency down-conversion inaccordance with the invention. For example, the FM intermediate signal2110 in FIG. 21D and the FM intermediate signal 2112 in FIG. 21Eillustrate that the FM carrier signal 816 was successfullydown-converted to an intermediate signal by retaining enough basebandinformation for sufficient reconstruction.

-   -   -   -   1.2.2.2 Structural Description

The operation of the under-sampling system 1602 is now described for theanalog FM carrier signal 716, with reference to the flowchart 1407 andthe timing diagrams of FIGS. 20A–E. In step 1408, the under-samplingmodule 1606 receives the FM carrier signal 716 (FIG. 20A). In step 1410,the under-sampling module 1606 receives the under-sampling signal 2006(FIG. 20C). In step 1412, the under-sampling module 1606 under-samplesthe FM carrier signal 716 at the aliasing rate of the under-samplingsignal 2006 to down-convert the FM carrier signal 716 to the FMintermediate signal 2012 (FIG. 20E).

The operation of the under-sampling system 1602 is now described for thedigital FM carrier signal 816, with reference to the flowchart 1407 andthe timing diagrams of FIGS. 21A–E. In step 1408, the under-samplingmodule 1606 receives the FM carrier signal 816 (FIG. 21A). In step 1410,the under-sampling module 1606 receives the under-sampling signal 2106(FIG. 21C). In step 1412, the under-sampling module 1606 under-samplesthe FM carrier signal 816 at the aliasing rate of the under-samplingsignal 2106 to down-convert the FM carrier signal 816 to the FMintermediate signal 2112 (FIG. 21E).

Example implementations of the under-sampling module 1606 are providedin Sections 4 and 5 below.

-   -   -   1.2.3 Third Example Embodiment: Phase Modulation            -   1.2.3.1 Operational Description

Operation of the exemplary process of the flowchart 1407 in FIG. 14B isdescribed below for the analog PM carrier signal 916, illustrated inFIG. 9C, and for the digital PM carrier signal 1016, illustrated in FIG.10C.

-   -   -   -   -   1.2.3.1.1 Analog PM Carrier Signal

A process for down-converting the analog PM carrier signal 916 to ananalog PM intermediate signal is now described with reference to theflowchart 1407 in FIG. 14B. The analog PM carrier signal 916 isre-illustrated in FIG. 23A for convenience. For this example, the analogPM carrier signal 916 oscillates at approximately 901 MHZ. In FIG. 23B,a PM carrier signal 2304 illustrates a portion of the analog PM carriersignal 916, from time t1 to t3, on an expanded time scale.

The process of down-converting the PM carrier signal 916 to a PMintermediate signal begins at step 1408, which includes receiving an EMsignal. This is represented in FIG. 23A, by the analog PM carrier signal916.

Step 1410 includes receiving an under-sampling signal having an aliasingrate F_(AR). FIG. 23C illustrates an example under-sampling signal 2306on approximately the same time scale as FIG. 23B. The under-samplingsignal 2306 includes a train of pulses 2307 having negligible aperturesthat tend towards zero time in duration. The pulses 2307 repeat at thealiasing rate, or pulse repetition rate, which is determined or selectedas previously described. Generally, when down-converting to anintermediate signal, the aliasing rate F_(AR) is substantially equal toa harmonic or, more typically, a sub-harmonic of the differencefrequency F_(DIFF). In this example, the aliasing rate is approximately450 MHZ.

Step 1412 includes under-sampling the EM signal at the aliasing rate todown-convert the EM signal to the intermediate signal F_(IF). Step 1412is illustrated in FIG. 23B by under-sample points 2305.

Because a harmonic of the aliasing rate is off-set from the PM carriersignal 916, the under-sample points 2305 occur at different locations ofsubsequent cycles of the PM carrier signal 916. As a result, theunder-sample points capture various amplitudes of the PM carrier signal916.

In FIG. 23D, voltage points 2308 correlate to the under-sample points2305. In an embodiment, the voltage points 2308 form an analog PMintermediate signal 2310. This can be accomplished in many ways. Forexample, each voltage point 2308 can be held at a relatively constantlevel until the next voltage point is received. This results in astair-step output which can be smoothed or filtered if desired, asdescribed below.

In FIG. 23E, an analog PM intermediate signal 2312 illustrates theanalog PM intermediate signal 2310, after filtering, on a compressedtime scale. Although FIG. 23E illustrates the PM intermediate signal2312 as a filtered output signal, the output signal does not need to befiltered or smoothed to be within the scope of the invention. Instead,the output signal can be tailored for different applications.

The analog PM intermediate signal 2312 is substantially similar to theanalog PM carrier signal 916, except that the analog PM intermediatesignal 2312 is at the 1 MHZ intermediate frequency. The analog PMintermediate signal 2312 can be demodulated through any conventional PMdemodulation technique.

The drawings referred to herein illustrate frequency down-conversion inaccordance with the invention. For example, the analog PM intermediatesignal 2310 in FIG. 23D and the analog PM intermediate signal 2312 inFIG. 23E illustrate that the analog PM carrier signal 2316 wassuccessfully down-converted to an intermediate signal by retainingenough baseband information for sufficient reconstruction.

-   -   -   -   -   1.2.3.1.2 Digital PM Carrier Signal

A process for down-converting the digital PM carrier signal 1016 to adigital PM intermediate signal is now described with reference to theflowchart 1407 in FIG. 14B. The digital PM carrier signal 1016 isre-illustrated in FIG. 22A for convenience. For this example, thedigital PM carrier signal 1016 oscillates at approximately 901 MHZ. InFIG. 22B, a PM carrier signal 2204 illustrates a portion of the digitalPM carrier signal 1016, from time t1 to t3, on an expanded time scale.

The process begins at step 1408, which includes receiving an EM signal.This is represented in FIG. 22A by the digital PM carrier signal 1016.

Step 1408 includes receiving an under-sampling signal having an aliasingrate F_(AR). FIG. 22C illustrates example under-sampling signal 2206 onapproximately the same time scale as FIG. 22B. The under-sampling signal2206 includes a train of pulses 2207 having negligible apertures thattend towards zero time in duration. The pulses 2207 repeat at thealiasing rate, or a pulse repetition rate, which is determined orselected as previously described. Generally, when down-converting to anintermediate signal, the aliasing rate F_(AR) is substantially equal toa harmonic or, more typically, a sub-harmonic of the differencefrequency F_(DIFF). In this example, the aliasing rate is approximately450 MHZ.

Step 1412 includes under-sampling the EM signal at the aliasing rate todown-convert the EM signal to an intermediate signal F_(IF). Step 1412is illustrated in FIG. 22B by under-sample points 2205.

Because a harmonic of the aliasing rate is off-set from the PM carriersignal 1016, the under-sample points 2205 occur at different locationsof subsequent cycles of the PM carrier signal 1016.

In FIG. 22D, voltage points 2208 correlate to the under-sample points2205. In an embodiment, the voltage points 2208 form a digital PMintermediate signal 2210. This can be accomplished in many ways. Forexample, each voltage point 2208 can be held at a relatively constantlevel until the next voltage point is received. This results in astair-step output which can be smoothed or filtered if desired, asdescribed below.

In FIG. 22E, a digital PM intermediate signal 2212 represents thedigital PM intermediate signal 2210 on a compressed time scale. AlthoughFIG. 22E illustrates the PM intermediate signal 2212 as a filteredoutput signal, the output signal does not need to be filtered orsmoothed to be within the scope of the invention. Instead, the outputsignal can be tailored for different applications.

The digital PM intermediate signal 2212 is substantially similar to thedigital PM carrier signal 1016, except that the digital PM intermediatesignal 2212 is at the 1 MHZ intermediate frequency. The digital PMcarrier signal 2212 can be demodulated through any conventional PMdemodulation technique.

The drawings referred to herein illustrate frequency down-conversion inaccordance with the invention. For example, the digital PM intermediatesignal 2210 in FIG. 22D and the digital PM intermediate signal 2212 inFIG. 22E illustrate that the digital PM carrier signal 1016 wassuccessfully down-converted to an intermediate signal by retainingenough baseband information for sufficient reconstruction.

-   -   -   -   1.2.3.2 Structural Description

The operation of the under-sampling system 1602 is now described for theanalog PM carrier signal 916, with reference to the flowchart 1407 andthe timing diagrams of FIGS. 23A–E. In step 1408, the under-samplingmodule 1606 receives the PM carrier signal 916 (FIG. 23A). In step 1410,the under-sampling module 1606 receives the under-sampling signal 2306(FIG. 23C). In step 1412, the under-sampling module 1606 under-samplesthe PM carrier signal 916 at the aliasing rate of the under-samplingsignal 2306 to down-convert the PM carrier signal 916 to the PMintermediate signal 2312 (FIG. 23E).

The operation of the under-sampling system 1602 is now described for thedigital PM carrier signal 1016, with reference to the flowchart 1407 andthe timing diagrams of FIGS. 22A–E. In step 1408, the under-samplingmodule 1606 receives the PM carrier signal 1016 (FIG. 22A). In step1410, the under-sampling module 1606 receives the under-sampling signal2206 (FIG. 22C). In step 1412, the under-sampling module 1606under-samples the PM carrier signal 1016 at the aliasing rate of theunder-sampling signal 2206 to down-convert the PM carrier signal 1016 tothe PM intermediate signal 2212 (FIG. 22E).

Example implementations of the under-sampling module 1606 are providedin Sections 4 and 5 below.

-   -   -   1.2.4 Other Embodiments

The embodiments described above are provided for purposes ofillustration. These embodiments are not intended to limit the invention.Alternate embodiments, differing slightly or substantially from thosedescribed herein, will be apparent to persons skilled in the relevantart(s) based on the teachings contained herein. Such alternateembodiments fall within the scope and spirit of the present invention.Example implementations of the under-sampling module 1606 are providedin Sections 4 and 5 below.

-   -   1.3 Implementation Examples

Exemplary operational and/or structural implementations related to themethod(s), structure(s), and/or embodiments described above arepresented in Sections 4 and 5 below. The implementations are presentedfor purposes of illustration, and not limitation. The invention is notlimited to the particular implementation examples described therein.Alternate implementations (including equivalents, extensions,variations, deviations, etc., of those described herein) will beapparent to persons skilled in the relevant art(s) based on theteachings contained herein. Such alternate implementations fall withinthe scope and spirit of the present invention.

2. Directly Down-Converting an EM Signal to a Baseband Signal(Direct-to-Data)

In an embodiment, the invention directly down-converts an EM signal to abaseband signal, by under-sampling the EM signal. This embodiment isreferred to herein as direct-to-data down-conversion and is illustratedin FIG. 45B as 4510.

This embodiment can be implemented with modulated and unmodulated EMsignals. This embodiment is described herein using the modulated carriersignal F_(MC) in FIG. 1, as an example. In the example, the modulatedcarrier signal F_(MC) is directly down-converted to the demodulatedbaseband signal F_(DMB). Upon reading the disclosure and examplestherein, one skilled in the relevant art(s) will understand that theinvention is applicable to down-convert any EM signal, including but notlimited to, modulated carrier signals and unmodulated carrier signals.

The following sections describe example methods for directlydown-converting the modulated carrier signal F_(MC) to the demodulatedbaseband signal F_(DMB). Exemplary structural embodiments forimplementing the methods are also described. It should be understoodthat the invention is not limited to the particular embodimentsdescribed below. Equivalents, extensions, variations, deviations, etc.,of the following will be apparent to persons skilled in the relevantart(s) based on the teachings contained herein. Such equivalents,extensions, variations, deviations, etc., are within the scope andspirit of the present invention.

The following sections include a high level discussion, exampleembodiments, and implementation examples.

-   -   2.1 High Level Description

This section (including its subsections) provides a high-leveldescription of directly down-converting the modulated carrier signalF_(MC) to the demodulated baseband signal F_(DMB), according to theinvention. In particular, an operational process of directlydown-converting the modulated carrier signal F_(MC) to the demodulatedbaseband signal F_(DMB) is described at a high-level. Also, a structuralimplementation for implementing this process is described at ahigh-level. The structural implementation is described herein forillustrative purposes, and is not limiting. In particular, the processdescribed in this section can be achieved using any number of structuralimplementations, one of which is described in this section. The detailsof such structural implementations will be apparent to persons skilledin the relevant art(s) based on the teachings contained herein.

-   -   -   2.1.1 Operational Description

FIG. 14C depicts a flowchart 1413 that illustrates an exemplary methodfor directly down-converting an EM signal to a demodulated basebandsignal F_(DMB). The exemplary method illustrated in the flowchart 1413is an embodiment of the flowchart 1401 in FIG. 14A.

Any and all combinations of modulation techniques are valid for thisinvention. For ease of discussion, the digital AM carrier signal 616 isused to illustrate a high level operational description of theinvention. Subsequent sections provide detailed descriptions for AM andPM example embodiments. FM presents special considerations that aredealt with separately in Section II.3, below. Upon reading thedisclosure and examples therein, one skilled in the relevant art(s) willunderstand that the invention can be implemented to down-convert anytype of EM signal, including any form of modulated carrier signal andunmodulated carrier signals.

The method illustrated in the flowchart 1413 is now described at a highlevel using the digital AM carrier signal 616, from FIG. 6C. The digitalAM carrier signal 616 is re-illustrated in FIG. 33A for convenience.

The process of the flowchart 1413 begins at step 1414, which includesreceiving an EM signal. Step 1414 is represented by the digital AMcarrier signal 616 in FIG. 33A.

Step 1416 includes receiving an under-sampling signal having an aliasingrate F_(AR). FIG. 33B illustrates an example under-sampling signal 3302which includes a train of pulses 3303 having negligible apertures thattend towards zero time in duration. The pulses 3303 repeat at thealiasing rate or pulse repetition rate. The aliasing rate is determinedin accordance with EQ. (2), reproduced below for convenience.F _(C) =n·F _(AR) ±F _(IF)  EQ. (2)

When directly down-converting an EM signal to baseband (i.e., zero IF),EQ. (2) becomes:F _(C) =n·F _(AR)  EQ. (8)Thus, to directly down-convert the AM signal 616 to a demodulatedbaseband signal, the aliasing rate is substantially equal to thefrequency of the AM signal 616 or to a harmonic or sub-harmonic thereof.Although the aliasing rate is too low to permit reconstruction of higherfrequency components of the AM signal 616 (i.e., the carrier frequency),it is high enough to permit substantial reconstruction of the lowerfrequency modulating baseband signal 310.

Step 1418 includes under-sampling the EM signal at the aliasing rate todirectly down-convert it to the demodulated baseband signal F_(DMB).FIG. 33C illustrates a stair step demodulated baseband signal 3304,which is generated by the direct down-conversion process. Thedemodulated baseband signal 3304 is similar to the digital modulatingbaseband signal 310 in FIG. 3.

FIG. 33D depicts a filtered demodulated baseband signal 3306, which canbe generated from the stair step demodulated baseband signal 3304. Theinvention can thus generate a filtered output signal, a partiallyfiltered output signal, or a relatively unfiltered stair step outputsignal. The choice between filtered, partially filtered and non-filteredoutput signals is generally a design choice that depends upon theapplication of the invention.

-   -   -   2.1.2 Structural Description

FIG. 16 illustrates the block diagram of the under-sampling system 1602according to an embodiment of the invention. The under-sampling system1602 is an example embodiment of the generic aliasing system 1302 inFIG. 13.

In a direct to data embodiment, the frequency of the under-samplingsignal 1604 is substantially equal to a harmonic of the EM signal 1304or, more typically, a sub-harmonic thereof. Preferably, theunder-sampling module 1606 under-samples the EM signal 1304 to directlydown-convert it to the demodulated baseband signal F_(DMB), in themanner shown in the operational flowchart 1413. But it should beunderstood that the scope and spirit of the invention includes otherstructural embodiments for performing the steps of the flowchart 1413.The specifics of the other structural embodiments will be apparent topersons skilled in the relevant art(s) based on the discussion containedherein.

The operation of the aliasing system 1602 is now described for thedigital AM carrier signal 616, with reference to the flowchart 1413 andto the timing diagrams in FIGS. 33A–D. In step 1414, the under-samplingmodule 1606 receives the AM carrier signal 616 (FIG. 33A). In step 1416,the under-sampling module 1606 receives the under-sampling signal 3302(FIG. 33B). In step 1418, the under-sampling module 1606 under-samplesthe AM carrier signal 616 at the aliasing rate of the under-samplingsignal 3302 to directly down-convert the AM carrier signal 616 to thedemodulated baseband signal 3304 in FIG. 33C or the filtered demodulatedbaseband signal 3306 in FIG. 33D.

Example implementations of the under-sampling module 1606 are providedin Sections 4 and 5 below.

-   -   2.2 Example Embodiments

Various embodiments related to the method(s) and structure(s) describedabove are presented in this section (and its subsections). Theseembodiments are described herein for purposes of illustration, and notlimitation. The invention is not limited to these embodiments. Alternateembodiments (including equivalents, extensions, variations, deviations,etc., of the embodiments described herein) will be apparent to personsskilled in the relevant art(s) based on the teachings contained herein.The invention is intended and adapted to include such alternateembodiments.

The method for down-converting the EM signal 1304 to the demodulatedbaseband signal F_(DMB), illustrated in the flowchart 1413 of FIG. 14C,can be implemented with any type EM signal, including modulated carriersignals, including but not limited to, AM, PM, etc., or any combinationthereof. Operation of the flowchart 1413 of FIG. 14C is described belowfor AM and PM carrier signals. The exemplary descriptions below areintended to facilitate an understanding of the present invention. Thepresent invention is not limited to or by the exemplary embodimentsbelow.

-   -   -   2.2.1 First Example Embodiment: Amplitude Modulation            -   2.2.1.1 Operational Description

Operation of the exemplary process of the flowchart 1413 in FIG. 14C isdescribed below for the analog AM carrier signal 516, illustrated inFIG. 5C and for the digital AM carrier signal 616, illustrated in FIG.6C.

-   -   -   -   -   2.2.1.1.1 Analog AM Carrier Signal

A process for directly down-converting the analog AM carrier signal 516to a demodulated baseband signal is now described with reference to theflowchart 1413 in FIG. 14C. The analog AM carrier signal 516 isre-illustrated in 35A for convenience. For this example, the analog AMcarrier signal 516 oscillates at approximately 900 MHZ. In FIG. 35B, ananalog AM carrier signal 3504 illustrates a portion of the analog AMcarrier signal 516 on an expanded time scale.

The process begins at step 1414, which includes receiving an EM signal.This is represented by the analog AM carrier signal 516.

Step 1416 includes receiving an under-sampling signal having an aliasingrate F_(AR). FIG. 35C illustrates an example under-sampling signal 3506on approximately the same time scale as FIG. 35B. The under-samplingsignal 3506 includes a train of pulses 3507 having negligible aperturesthat tend towards zero time in duration. The pulses 3507 repeat at thealiasing rate or pulse repetition rate, which is determined or selectedas previously described. Generally, when directly down-converting to ademodulated baseband signal, the aliasing rate F_(AR) is substantiallyequal to a harmonic or, more typically, a sub-harmonic of theunder-sampled signal. In this example, the aliasing rate isapproximately 450 MHZ.

Step 1418 includes under-sampling the EM signal at the aliasing rate todirectly down-convert it to the demodulated baseband signal F_(DMB).Step 1418 is illustrated in FIG. 35B by under-sample points 3505.Because a harmonic of the aliasing rate is substantially equal to thefrequency of the signal 516, essentially no IF is produced. The onlysubstantial aliased component is the baseband signal.

In FIG. 35D, voltage points 3508 correlate to the under-sample points3505. In an embodiment, the voltage points 3508 form a demodulatedbaseband signal 3510. This can be accomplished in many ways. Forexample, each voltage point 3508 can be held at a relatively constantlevel until the next voltage point is received. This results in astair-step output which can be smoothed or filtered if desired, asdescribed below.

In FIG. 35E, a demodulated baseband signal 3512 represents thedemodulated baseband signal 3510, after filtering, on a compressed timescale. Although FIG. 35E illustrates the demodulated baseband signal3512 as a filtered output signal, the output signal does not need to befiltered or smoothed to be within the scope of the invention. Instead,the output signal can be tailored for different applications.

The demodulated baseband signal 3512 is substantially similar to themodulating baseband signal 210. The demodulated baseband signal 3512 canbe processed using any signal processing technique(s) without furtherdown-conversion or demodulation.

The aliasing rate of the under-sampling signal is preferably controlledto optimize the demodulated baseband signal for amplitude output andpolarity, as desired.

In the example above, the under-sample points 3505 occur at positivelocations of the AM carrier signal 516. Alternatively, the under-samplepoints 3505 can occur at other locations including negative points ofthe analog AM carrier signal 516. When the under-sample points 3505occur at negative locations of the AM carrier signal 516, the resultantdemodulated baseband signal is inverted relative to the modulatingbaseband signal 210.

The drawings referred to herein illustrate direct to datadown-conversion in accordance with the invention. For example, thedemodulated baseband signal 3510 in FIG. 35D and the demodulatedbaseband signal 3512 in FIG. 35E illustrate that the AM carrier signal516 was successfully down-converted to the demodulated baseband signal3510 by retaining enough baseband information for sufficientreconstruction.

-   -   -   -   -   2.2.1.1.2 Digital AM Carrier Signal

A process for directly down-converting the digital AM carrier signal 616to a demodulated baseband signal is now described with reference to theflowchart 1413 in FIG. 14C. The digital AM carrier signal 616 isre-illustrated in FIG. 36A for convenience. For this example, thedigital AM carrier signal 616 oscillates at approximately 901 MHZ. InFIG. 36B, a digital AM carrier signal 3604 illustrates a portion of thedigital AM carrier signal 616 on an expanded time scale.

The process begins at step 1414, which includes receiving an EM signal.This is represented by the digital AM carrier signal 616.

Step 1416 includes receiving an under-sampling signal having an aliasingrate F_(AR). FIG. 36C illustrates an example under-sampling signal 3606on approximately the same time scale as FIG. 36B. The under-samplingsignal 3606 includes a train of pulses 3607 having negligible aperturesthat tend towards zero time in duration. The pulses 3607 repeat at thealiasing rate or pulse repetition rate, which is determined or selectedas previously described. Generally, when directly down-converting to ademodulated baseband signal, the aliasing rate F_(AR) is substantiallyequal to a harmonic or, more typically, a sub-harmonic of theunder-sampled signal. In this example, the aliasing rate isapproximately 450 MHZ.

Step 1418 includes under-sampling the EM signal at the aliasing rate todirectly down-convert it to the demodulated baseband signal F_(DMB).Step 1418 is illustrated in FIG. 36B by under-sample points 3605.Because the aliasing rate is substantially equal to the AM carriersignal 616, or to a harmonic or sub-harmonic thereof, essentially no IFis produced. The only substantial aliased component is the basebandsignal.

In FIG. 36D, voltage points 3608 correlate to the under-sample points3605. In an embodiment, the voltage points 3608 form a demodulatedbaseband signal 3610. This can be accomplished in many ways. Forexample, each voltage point 3608 can be held at a relatively constantlevel until the next voltage point is received. This results in astair-step output which can be smoothed or filtered if desired, asdescribed below.

In FIG. 36E, a demodulated baseband signal 3612 represents thedemodulated baseband signal 3610, after filtering, on a compressed timescale. Although FIG. 36E illustrates the demodulated baseband signal3612 as a filtered output signal, the output signal does not need to befiltered or smoothed to be within the scope of the invention. Instead,the output signal can be tailored for different applications.

The demodulated baseband signal 3612 is substantially similar to thedigital modulating baseband signal 310. The demodulated analog basebandsignal 3612 can be processed using any signal processing technique(s)without further down-conversion or demodulation.

The aliasing rate of the under-sampling signal is preferably controlledto optimize the demodulated baseband signal for amplitude output andpolarity, as desired.

In the example above, the under-sample points 3605 occur at positivelocations of signal portion 3604. Alternatively, the under-sample points3605 can occur at other locations including negative locations of thesignal portion 3604. When the under-sample points 3605 occur at negativepoints, the resultant demodulated baseband signal is inverted withrespect to the modulating baseband signal 310.

The drawings referred to herein illustrate frequency down-conversion inaccordance with the invention. For example, the demodulated basebandsignal 3610 in FIG. 36D and the demodulated baseband signal 3612 in FIG.36E illustrate that the digital AM carrier signal 616 was successfullydown-converted to the demodulated baseband signal 3610 by retainingenough baseband information for sufficient reconstruction.

-   -   -   -   2.2.1.2 Structural Description

The operation of the under-sampling module 1606 is now described for theanalog AM carrier signal 516, with reference to the flowchart 1413 andthe timing diagrams of FIGS. 35A–E. In step 1414, the under-samplingmodule 1606 receives the analog AM carrier signal 516 (FIG. 35A). Instep 1416, the under-sampling module 1606 receives the under-samplingsignal 3506 (FIG. 35C). In step 1418, the under-sampling module 1606under-samples the analog AM carrier signal 516 at the aliasing rate ofthe under-sampling signal 3506 to directly to down-convert the AMcarrier signal 516 to the demodulated analog baseband signal 3510 inFIG. 35D or to the filtered demodulated analog baseband signal 3512 inFIG. 35E.

The operation of the under-sampling system 1602 is now described for thedigital AM carrier signal 616, with reference to the flowchart 1413 andthe timing diagrams of FIGS. 36A–E. In step 1414, the under-samplingmodule 1606 receives the digital AM carrier signal 616 (FIG. 36A). Instep 1416, the under-sampling module 1606 receives the under-samplingsignal 3606 (FIG. 36C). In step 1418, the under-sampling module 1606under-samples the digital AM carrier signal 616 at the aliasing rate ofthe under-sampling signal 3606 to down-convert the digital AM carriersignal 616 to the demodulated digital baseband signal 3610 in FIG. 36Dor to the filtered demodulated digital baseband signal 3612 in FIG. 36E.

Example implementations of the under-sampling module 1606 are providedin Sections 4 and 5 below.

-   -   -   2.2.2 Second Example Embodiment: Phase Modulation            -   2.2.2.1 Operational Description

Operation of the exemplary process of the flowchart 1413 in FIG. 14C isdescribed below for the analog PM carrier signal 916, illustrated inFIG. 9C, and for the digital PM carrier signal 1016, illustrated in FIG.10C.

-   -   -   -   -   2.2.2.1.1 Analog PM Carrier Signal

A process for directly down-converting the analog PM carrier signal 916to a demodulated baseband signal is now described with reference to theflowchart 1413 in FIG. 14C. The analog PM carrier signal 916 isre-illustrated in 37A for convenience. For this example, the analog PMcarrier signal 916 oscillates at approximately 900 MHZ. In FIG. 37B, ananalog PM carrier signal 3704 illustrates a portion of the analog PMcarrier signal 916 on an expanded time scale.

The process begins at step 1414, which includes receiving an EM signal.This is represented by the analog PM signal 916.

Step 1416 includes receiving an under-sampling signal having an aliasingrate F_(AR) FIG. 37C illustrates an example under-sampling signal 3706on approximately the same time scale as FIG. 37B. The under-samplingsignal 3706 includes a train of pulses 3707 having negligible aperturesthat tend towards zero time in duration. The pulses 3707 repeat at thealiasing rate or pulse repetition rate, which is determined or selectedas previously described. Generally, when directly down-converting to ademodulated baseband signal, the aliasing rate F_(AR) is substantiallyequal to a harmonic or, more typically, a sub-harmonic of theunder-sampled signal. In this example, the aliasing rate isapproximately 450 MHZ.

Step 1418 includes under-sampling the analog PM carrier signal 916 atthe aliasing rate to directly down-convert it to a demodulated basebandsignal. Step 1418 is illustrated in FIG. 37B by under-sample points3705.

Because a harmonic of the aliasing rate is substantially equal to thefrequency of the signal 916, or substantially equal to a harmonic orsub-harmonic thereof, essentially no IF is produced. The onlysubstantial aliased component is the baseband signal.

In FIG. 37D, voltage points 3708 correlate to the under-sample points3705. In an embodiment, the voltage points 3708 form a demodulatedbaseband signal 3710. This can be accomplished in many ways. Forexample, each voltage point 3708 can be held at a relatively constantlevel until the next voltage point is received. This results in astair-step output which can be smoothed or filtered if desired, asdescribed below.

In FIG. 37E, a demodulated baseband signal 3712 represents thedemodulated baseband signal 3710, after filtering, on a compressed timescale. Although FIG. 37E illustrates the demodulated baseband signal3712 as a filtered output signal, the output signal does not need to befiltered or smoothed to be within the scope of the invention. Instead,the output signal can be tailored for different applications.

The demodulated baseband signal 3712 is substantially similar to theanalog modulating baseband signal 210. The demodulated baseband signal3712 can be processed without further down-conversion or demodulation.

The aliasing rate of the under-sampling signal is preferably controlledto optimize the demodulated baseband signal for amplitude output andpolarity, as desired.

In the example above, the under-sample points 3705 occur at positivelocations of the analog PM carrier signal 916. Alternatively, theunder-sample points 3705 can occur at other locations include negativepoints of the analog PM carrier signal 916. When the under-sample points3705 occur at negative locations of the analog PM carrier signal 916,the resultant demodulated baseband signal is inverted relative to themodulating baseband signal 210.

The drawings referred to herein illustrate direct to datadown-conversion in accordance with the invention. For example, thedemodulated baseband signal 3710 in FIG. 37D and the demodulatedbaseband signal 3712 in FIG. 37E illustrate that the analog PM carriersignal 916 was successfully down-converted to the demodulated basebandsignal 3710 by retaining enough baseband information for sufficientreconstruction.

-   -   -   -   -   2.2.2.1.2 Digital PM Carrier Signal

A process for directly down-converting the digital PM carrier signal1016 to a demodulated baseband signal is now described with reference tothe flowchart 1413 in FIG. 14C. The digital PM carrier signal 1016 isre-illustrated in 38A for convenience. For this example, the digital PMcarrier signal 1016 oscillates at approximately 900 MHZ. In FIG. 38B, adigital PM carrier signal 3804 illustrates a portion of the digital PMcarrier signal 1016 on an expanded time scale.

The process begins at step 1414, which includes receiving an EM signal.This is represented by the digital PM signal 1016.

Step 1416 includes receiving an under-sampling signal having an aliasingrate F_(AR). FIG. 38C illustrates an example under-sampling signal 3806on approximately the same time scale as FIG. 38B. The under-samplingsignal 3806 includes a train of pulses 3807 having negligible aperturesthat tend towards zero time in duration. The pulses 3807 repeat at thealiasing rate or pulse repetition rate, which is determined or selectedas described above. Generally, when directly down-converting to ademodulated baseband signal, the aliasing rate F_(AR) is substantiallyequal to a harmonic or, more typically, a sub-harmonic of theunder-sampled signal. In this example, the aliasing rate isapproximately 450 MHZ.

Step 1418 includes under-sampling the digital PM carrier signal 1016 atthe aliasing rate to directly down-convert it to a demodulated basebandsignal. This is illustrated in FIG. 38B by under-sample points 3705.

Because a harmonic of the aliasing rate is substantially equal to thefrequency of the signal 1016, essentially no IF is produced. The onlysubstantial aliased component is the baseband signal.

In FIG. 38D, voltage points 3808 correlate to the under-sample points3805. In an embodiment, the voltage points 3808 form a demodulatedbaseband signal 3810. This can be accomplished in many ways. Forexample, each voltage point 3808 can be held at a relatively constantlevel until the next voltage point is received. This results in astair-step output which can be smoothed or filtered if desired, asdescribed below.

In FIG. 38E, a demodulated baseband signal 3812 represents thedemodulated baseband signal 3810, after filtering, on a compressed timescale. Although FIG. 38E illustrates the demodulated baseband signal3812 as a filtered output signal, the output signal does not need to befiltered or smoothed to be within the scope of the invention. Instead,the output signal can be tailored for different applications.

The demodulated baseband signal 3812 is substantially similar to thedigital modulating baseband signal 310. The demodulated baseband signal3812 can be processed without further down-conversion or demodulation.

The aliasing rate of the under-sampling signal is preferably controlledto optimize the demodulated baseband signal for amplitude output andpolarity, as desired.

In the example above, the under-sample points 3805 occur at positivelocations of the digital PM carrier signal 1016. Alternatively, theunder-sample points 3805 can occur at other locations include negativepoints of the digital PM carrier signal 1016. When the under-samplepoints 3805 occur at negative locations of the digital PM carrier signal1016, the resultant demodulated baseband signal is inverted relative tothe modulating baseband signal 310.

The drawings referred to herein illustrate frequency down-conversion inaccordance with the invention. For example, the demodulated basebandsignal 3810 in FIG. 38D and the demodulated baseband signal 3812 in FIG.38E illustrate that the digital PM carrier signal 1016 was successfullydown-converted to the demodulated baseband signal 3810 by retainingenough baseband information for sufficient reconstruction.

-   -   -   -   2.2.1.2 Structural Description

The operation of the under-sampling system 1602 is now described for theanalog PM carrier signal 916, with reference to the flowchart 1413 andthe timing diagrams of FIGS. 37A–E. In step 1414, the under-samplingmodule 1606 receives the analog PM carrier signal 916 (FIG. 37A). Instep 1416, the under-sampling module 1606 receives the under-samplingsignal 3706 (FIG. 37C). In step 1418, the under-sampling module 1606under-samples the analog PM carrier signal 916 at the aliasing rate ofthe under-sampling signal 3706 to down-convert the PM carrier signal 916to the demodulated analog baseband signal 3710 in FIG. 37D or to thefiltered demodulated analog baseband signal 3712 in FIG. 37E.

The operation of the under-sampling system 1602 is now described for thedigital PM carrier signal 1016, with reference to the flowchart 1413 andthe timing diagrams of FIGS. 38A–E. In step 1414, the under-samplingmodule 1606 receives the digital PM carrier signal 1016 (FIG. 38A). Instep 1416, the under-sampling module 1606 receives the under-samplingsignal 3806 (FIG. 38C). In step 1418, the under-sampling module 1606under-samples the digital PM carrier signal 1016 at the aliasing rate ofthe under-sampling signal 3806 to down-convert the digital PM carriersignal 1016 to the demodulated digital baseband signal 3810 in FIG. 38Dor to the filtered demodulated digital baseband signal 3812 in FIG. 38E.

-   -   -   2.2.3 Other Embodiments

The embodiments described above are provided for purposes ofillustration. These embodiments are not intended to limit the invention.Alternate embodiments, differing slightly or substantially from thosedescribed herein, will be apparent to persons skilled in the relevantart(s) based on the teachings contained herein. Such alternateembodiments fall within the scope and spirit of the present invention.

-   -   2.3 Implementation Examples

Exemplary operational and/or structural implementations related to themethod(s), structure(s), and/or embodiments described above arepresented in Sections 4 and 5 below. These implementations are presentedfor purposes of illustration, and not limitation. The invention is notlimited to the particular implementation examples described therein.Alternate implementations (including equivalents, extensions,variations, deviations, etc., of those described herein) will beapparent to persons skilled in the relevant art(s) based on theteachings contained herein. Such alternate implementations fall withinthe scope and spirit of the present invention.

3. Modulation Conversion

In an embodiment, the invention down-converts an FM carrier signalF_(FMC) to a non-FM signal F_((NON-FM)), by under-sampling the FMcarrier signal F_(FMC). This embodiment is illustrated in FIG. 45B as4512.

In an example embodiment, the FM carrier signal F_(FMC) isdown-converted to a phase modulated (PM) signal FPM. In another exampleembodiment, the FM carrier signal F_(FMC) is down-converted to anamplitude modulated (AM) signal F_(AM). The invention is not limited tothese embodiments. The down-converted signal can be demodulated with anyconventional demodulation technique to obtain a demodulated basebandsignal F_(DMB).

The invention can be implemented with any type of FM signal. Exemplaryembodiments are provided below for down-converting a frequency shiftkeying (FSK) signal to a non-FSK signal. FSK is a sub-set of FM, whereinan FM signal shifts or switches between two or more frequencies. FSK istypically used for digital modulating baseband signals, such as thedigital modulating baseband signal 310 in FIG. 3. For example, in FIG.8, the digital FM signal 816 is an FSK signal that shifts between anupper frequency and a lower frequency, corresponding to amplitude shiftsin the digital modulating baseband signal 310. The FSK signal 816 isused in example embodiments below.

In a first example embodiment, the FSK signal 816 is under-sampled at analiasing rate that is based on a mid-point between the upper and lowerfrequencies of the FSK signal 816. When the aliasing rate is based onthe mid-point, the FSK signal 816 is down-converted to a phase shiftkeying (PSK) signal. PSK is a sub-set of phase modulation, wherein a PMsignal shifts or switches between two or more phases. PSK is typicallyused for digital modulating baseband signals. For example, in FIG. 10,the digital PM signal 1016 is a PSK signal that shifts between twophases. The PSK signal 1016 can be demodulated by any conventional PSKdemodulation technique(s).

In a second example embodiment, the FSK signal 816 is under-sampled atan aliasing rate that is based upon either the upper frequency or thelower frequency of the FSK signal 816. When the aliasing rate is basedupon the upper frequency or the lower frequency of the FSK signal 816,the FSK signal 816 is down-converted to an amplitude shift keying (ASK)signal. ASK is a sub-set of amplitude modulation, wherein an AM signalshifts or switches between two or more amplitudes. ASK is typically usedfor digital modulating baseband signals. For example, in FIG. 6, thedigital AM signal 616 is an ASK signal that shifts between the firstamplitude and the second amplitude. The ASK signal 616 can bedemodulated by any conventional ASK demodulation technique(s).

The following sections describe methods for under-sampling an FM carriersignal F_(FMC) to down-convert it to the non-FM signal F_((NON-FM)).Exemplary structural embodiments for implementing the methods are alsodescribed. It should be understood that the invention is not limited tothe particular embodiments described below. Equivalents, extensions,variations, deviations, etc., of the following will be apparent topersons skilled in the relevant art(s) based on the teachings containedherein. Such equivalents, extensions, variations, deviations, etc., arewithin the scope and spirit of the present invention.

The following sections include a high level discussion, exampleembodiments, and implementation examples.

-   -   3.1 High Level Description

This section (including its subsections) provides a high-leveldescription of under-sampling the FM carrier signal F_(FM) todown-convert it to the non-FM signal F_((NON-FM)), according to theinvention. In particular, an operational process for down-converting theFM carrier signal F_(FM) to the non-FM signal F_((NON-FM)) is describedat a high-level. Also, a structural implementation for implementing thisprocess is described at a high-level. The structural implementation isdescribed herein for illustrative purposes, and is not limiting. Inparticular, the process described in this section can be achieved usingany number of structural implementations, one of which is described inthis section. The details of such structural implementations will beapparent to persons skilled in the relevant art(s) based on theteachings contained herein.

-   -   -   3.1.1 Operational Description

FIG. 14D depicts a flowchart 1419 that illustrates an exemplary methodfor down-converting the FM carrier signal F_(FMC) to the non-FM signalF_((NON-FM)). The exemplary method illustrated in the flowchart 1419 isan embodiment of the flowchart 1401 in FIG. 14A.

Any and all forms of frequency modulation techniques are valid for thisinvention. For ease of discussion, the digital FM carrier (FSK) signal816 is used to illustrate a high level operational description of theinvention. Subsequent sections provide detailed flowcharts anddescriptions for the FSK signal 816. Upon reading the disclosure andexamples therein, one skilled in the relevant art(s) will understandthat the invention can be implemented to down-convert any type of FMsignal.

The method illustrated in the flowchart 1419 is described below at ahigh level for down-converting the FSK signal 816 in FIG. 8C to a PSKsignal. The FSK signal 816 is re-illustrated in FIG. 39A forconvenience.

The process of the flowchart 1419 begins at step 1420, which includesreceiving an FM signal. This is represented by the FSK signal 816. TheFSK signal 816 shifts between an upper frequency 3910 and a lowerfrequency 3912. In an exemplary embodiment, the upper frequency 3910 isapproximately 901 MHZ and the lower frequency 3912 is approximately 899MHZ.

Step 1422 includes receiving an under-sampling signal having an aliasingrate F_(AR). FIG. 39B illustrates an example under-sampling signal 3902which includes a train of pulses 3903 having negligible apertures thattend towards zero time in duration. The pulses 3903 repeat at thealiasing rate or pulse repetition rate.

When down-converting an FM carrier signal F_(FMC) to a non-FM signalF_((NON-FM)), the aliasing rate is substantially equal to a frequencycontained within the FM signal, or substantially equal to a harmonic orsub-harmonic thereof. In this example overview embodiment, where the FSKsignal 816 is to be down-converted to a PSK signal, the aliasing rate isbased on a mid-point between the upper frequency 3910 and the lowerfrequency 3912. For this example, the mid-point is approximately 900MHZ. In another embodiment described below, where the FSK signal 816 isto be down-converted to an ASK signal, the aliasing rate is based oneither the upper frequency 3910 or the lower frequency 3912, not themid-point.

Step 1424 includes under-sampling the FM signal F_(FMC) at the aliasingrate to down-convert the FM carrier signal F_(FMC) to the non-FM signalF_((NON-FM)). Step 1424 is illustrated in FIG. 39C, which illustrates astair step PSK signal 3904, which is generated by the modulationconversion process.

When the upper frequency 3910 is under-sampled, the PSK signal 3904 hasa frequency of approximately 1 MHZ and is used as a phase reference.When the lower frequency 3912 is under-sampled, the PSK signal 3904 hasa frequency of 1 MHZ and is phase shifted 180 degrees from the phasereference.

FIG. 39D depicts a PSK signal 3906, which is a filtered version of thePSK signal 3904. The invention can thus generate a filtered outputsignal, a partially filtered output signal, or a relatively unfilteredstair step output signal. The choice between filtered, partiallyfiltered and non-filtered output signals is generally a design choicethat depends upon the application of the invention.

The aliasing rate of the under-sampling signal is preferably controlledto optimize the down-converted signal for amplitude output and polarity,as desired.

Detailed exemplary embodiments for down-converting an FSK signal to aPSK signal and for down-converting an FSK signal to an ASK signal areprovided below.

-   -   -   3.1.2 Structural Description

FIG. 16 illustrates the block diagram of the under-sampling system 1602according to an embodiment of the invention. The under-sampling system1602 includes the under-sampling module 1606. The under-sampling system1602 is an example embodiment of the generic aliasing system 1302 inFIG. 13.

In a modulation conversion embodiment, the EM signal 1304 is an FMcarrier signal and the under-sampling module 1606 under-samples the FMcarrier signal at a frequency that is substantially equal to a harmonicof a frequency within the FM signal or, more typically, substantiallyequal to a sub-harmonic of a frequency within the FM signal. Preferably,the under-sampling module 1606 under-samples the FM carrier signalF_(FMC) to down-convert it to a non-FM signal F_((NON-FM)) in the mannershown in the operational flowchart 1419. But it should be understoodthat the scope and spirit of the invention includes other structuralembodiments for performing the steps of the flowchart 1419. Thespecifics of the other structural embodiments will be apparent topersons skilled in the relevant art(s) based on the discussion containedherein.

The operation of the under-sampling system 1602 shall now be describedwith reference to the flowchart 1419 and the timing diagrams of FIGS.39A–39D. In step 1420, the under-sampling module 1606 receives the FSKsignal 816. In step 1422, the under-sampling module 1606 receives theunder-sampling signal 3902. In step 1424, the under-sampling module 1606under-samples the FSK signal 816 at the aliasing rate of theunder-sampling signal 3902 to down-convert the FSK signal 816 to the PSKsignal 3904 or 3906.

Example implementations of the under-sampling module 1606 are providedin Section 4 below.

-   -   3.2 Example Embodiments

Various embodiments related to the method(s) and structure(s) describedabove are presented in this section (and its subsections). Theseembodiments are described herein for purposes of illustration, and notlimitation. The invention is not limited to these embodiments. Alternateembodiments (including equivalents, extensions, variations, deviations,etc., of the embodiments described herein) will be apparent to personsskilled in the relevant art(s) based on the teachings contained herein.The invention is intended and adapted to include such alternateembodiments.

The method for down-converting an FM carrier signal F_(FMC) to a non-FMsignal, F_((NON-FM)), illustrated in the flowchart 1419 of FIG. 14D, canbe implemented with any type of FM carrier signal including, but notlimited to, FSK signals. The flowchart 1419 is described in detail belowfor down-converting an FSK signal to a PSK signal and fordown-converting a PSK signal to an ASK signal. The exemplarydescriptions below are intended to facilitate an understanding of thepresent invention. The present invention is not limited to or by theexemplary embodiments below.

-   -   -   3.2.1 First Example Embodiment: Down-Converting an FM Signal            to a PM Signal            -   3.2.1.1 Operational Description

Operation of the exemplary process of the flowchart 1419 in FIG. 14D isnow described for down-converting the FSK signal 816 illustrated in FIG.8C to a PSK signal. The FSK signal 816 is re-illustrated in FIG. 40A forconvenience.

The FSK signal 816 shifts between a first frequency 4006 and a secondfrequency 4008. In the exemplary embodiment, the first frequency 4006 islower than the second frequency 4008. In an alternative embodiment, thefirst frequency 4006 is higher than the second frequency 4008. For thisexample, the first frequency 4006 is approximately 899 MHZ and thesecond frequency 4008 is approximately 901 MHZ.

FIG. 40B illustrates an FSK signal portion 4004 that represents aportion of the FSK signal 816 on an expanded time scale.

The process of down-converting the FSK signal 816 to a PSK signal beginsat step 1420, which includes receiving an FM signal. This is representedby the FSK signal 816.

Step 1422 includes receiving an under-sampling signal having an aliasingrate F_(AR). FIG. 40C illustrates an example under-sampling signal 4007on approximately the same time scale as FIG. 40B. The under-samplingsignal 4007 includes a train of pulses 4009 having negligible aperturesthat tend towards zero time in duration. The pulses 4009 repeat at thealiasing rate, which is determined or selected as described above.Generally, when down-converting an FM signal to a non-FM signal, thealiasing rate is substantially equal to a harmonic or, more typically, asub-harmonic of a frequency contained within the FM signal.

In this example, where an FSK signal is being down-converted to a PSKsignal, the aliasing rate is substantially equal to a harmonic of themid-point between the frequencies 4006 and 4008 or, more typically,substantially equal to a sub-harmonic of the mid-point between thefrequencies 4006 and 4008. In this example, where the first frequency4006 is 899 MHZ and second frequency 4008 is 901 MHZ, the mid-point isapproximately 900 MHZ. Suitable aliasing rates include 1.8 GHZ, 900 MHZ,450 MHZ, etc. In this example, the aliasing rate of the under-samplingsignal 4008 is approximately 450 MHZ.

Step 1424 includes under-sampling the FM signal at the aliasing rate todown-convert it to the non-FM signal F_((NON-FM)). Step 1424 isillustrated in FIG. 40B by under-sample points 4005. The under-samplepoints 4005 occur at the aliasing rate of the pulses 4009.

In FIG. 40D, voltage points 4010 correlate to the under-sample points4005. In an embodiment, the voltage points 4010 form a PSK signal 4012.This can be accomplished in many ways. For example, each voltage point4010 can be held at a relatively constant level until the next voltagepoint is received. This results in a stair-step output which can besmoothed or filtered if desired, as described below.

When the first frequency 4006 is under-sampled, the PSK signal 4012 hasa frequency of approximately 1 MHZ and is used as a phase reference.When the second frequency 4008 is under-sampled, the PSK signal 4012 hasa frequency of 1 MHZ and is phase shifted 180 degrees from the phasereference.

In FIG. 40E, a PSK signal 4014 illustrates the PSK signal 4012, afterfiltering, on a compressed time scale. Although FIG. 40E illustrates thePSK signal 4012 as a filtered output signal 4014, the output signal doesnot need to be filtered or smoothed to be within the scope of theinvention. Instead, the output signal can be tailored for differentapplications. The PSK signal 4014 can be demodulated through anyconventional phase demodulation technique.

The aliasing rate of the under-sampling signal is preferably controlledto optimize the down-converted signal for amplitude output and polarity,as desired.

In the example above, the under-sample points 4005 occur at positivelocations of the FSK signal 816. Alternatively, the under-sample points4005 can occur at other locations including negative points of the FSKsignal 816. When the under-sample points 4005 occur at negativelocations of the FSK signal 816, the resultant PSK signal is invertedrelative to the PSK signal 4014.

The drawings referred to herein illustrate modulation conversion inaccordance with the invention. For example, the PSK signal 4014 in FIG.40E illustrates that the FSK signal 816 was successfully down-convertedto the PSK signal 4012 and 4014 by retaining enough baseband informationfor sufficient reconstruction.

-   -   -   -   3.2.1.2 Structural Description

The operation of the under-sampling system 1602 is now described fordown-converting the FSK signal 816 to a PSK signal, with reference tothe flowchart 1419 and to the timing diagrams of FIGS. 40A–E. In step1420, the under-sampling module 1606 receives the FSK signal 816 (FIG.40A). In step 1422, the under-sampling module 1606 receives theunder-sampling signal 4007 (FIG. 40C). In step 1424, the under-samplingmodule 1606 under-samples the FSK signal 816 at the aliasing rate of theunder-sampling signal 4007 to down-convert the FSK signal 816 to the PSKsignal 4012 in FIG. 40D or the PSK signal 4014 in FIG. 40E.

-   -   -   3.2.2 Second Example Embodiment: Down-Converting an FM            Signal to an AM Signal            -   3.2.2.1 Operational Description

Operation of the exemplary process of FIG. 14D is now described fordown-converting the FSK signal 816, illustrated in FIG. 8C, to an ASKsignal. The FSK signal 816 is re-illustrated in FIG. 41A forconvenience.

The FSK signal 816 shifts between a first frequency 4106 and a secondfrequency 4108. In the exemplary embodiment, the first frequency 4106 islower than the second frequency 4108. In an alternative embodiment, thefirst frequency 4106 is higher than the second frequency 4108. For thisexample, the first frequency 4106 is approximately 899 MHZ and thesecond frequency 4108 is approximately 901 MHZ.

FIG. 41B illustrates an FSK signal portion 4104 that represents aportion of the FSK signal 816 on an expanded time scale.

The process of down-converting the FSK signal 816 to an ASK signalbegins at step 1420, which includes receiving an FM signal. This isrepresented by the FSK signal 816.

Step 1422 includes receiving an under-sampling signal having an aliasingrate F_(AR). FIG. 41C illustrates an example under-sampling signal 4107illustrated on approximately the same time scale as FIG. 42B. Theunder-sampling signal 4107 includes a train of pulses 4109 havingnegligible apertures that tend towards zero time in duration. The pulses4109 repeat at the aliasing rate, or pulse repetition rate. The aliasingrate is determined or selected as described above.

Generally, when down-converting an FM signal to a non-FM signal, thealiasing rate is substantially equal to a harmonic of a frequency withinthe FM signal or, more typically, to a sub-harmonic of a frequencywithin the FM signal. When an FSK signal 816 is being down-converted toan ASK signal, the aliasing rate is substantially equal to a harmonic ofthe first frequency 4106 or the second frequency 4108 or, moretypically, substantially equal to a sub-harmonic of the first frequency4106 or the second frequency 4108. In this example, where the firstfrequency 4106 is 899 MHZ and the second frequency 4108 is 901 MHZ, thealiasing rate can be substantially equal to a harmonic or sub-harmonicof 899 MHZ or 901 MHZ. In this example the aliasing rate isapproximately 449.5 MHZ, which is a sub-harmonic of the first frequency4106.

Step 1424 includes under-sampling the FM signal at the aliasing rate todown-convert it to a non-FM signal F_((NON-FM)). Step 1424 isillustrated in FIG. 41B by under-sample points 4105. The under-samplepoints 4105 occur at the aliasing rate of the pulses 4109. When thefirst frequency 4106 is under-sampled, the aliasing pulses 4109 and theunder-sample points 4105 occur at the same location of subsequent cyclesof the FSK signal 816. This generates a relatively constant outputlevel. But when the second frequency 4108 is under-sampled, the aliasingpulses 4109 and the under-sample points 4005 occur at differentlocations of subsequent cycles of the FSK signal 816. This generates anoscillating pattern at approximately (901 MHZ−899 MHZ)=2 MHZ.

In FIG. 41D, voltage points 4110 correlate to the under-sample points4105. In an embodiment, the voltage points 4110 form an ASK signal 4112.This can be accomplished in many ways. For example, each voltage point4110 can be held at a relatively constant level until the next voltagepoint is received. This results in a stair-step output which can besmoothed or filtered if desired, as described below.

In FIG. 41E, an ASK signal 4114 illustrates the ASK signal 4112, afterfiltering, on a compressed time scale. Although FIG. 41E illustrates theASK signal 4114 as a filtered output signal, the output signal does notneed to be filtered or smoothed to be within the scope of the invention.Instead, the output signal can be tailored for different applications.The ASK signal 4114 can be demodulated through any conventionalamplitude demodulation technique.

When down-converting from FM to AM, the aliasing rate of theunder-sampling signal is preferably controlled to optimize thedemodulated baseband signal for amplitude output and/or polarity, asdesired.

In an alternative embodiment, the aliasing rate is based on the secondfrequency and the resultant ASK signal is reversed relative to the ASKsignal 4114.

The drawings referred to herein illustrate modulation conversion inaccordance with the invention. For example, the ASK signal 4114 in FIG.41E illustrates that the FSK carrier signal 816 was successfullydown-converted to the ASK signal 4114 by retaining enough basebandinformation for sufficient reconstruction.

-   -   -   -   3.2.2.2 Structural Description

The operation of the under-sampling system 1602 is now described fordown-converting the FSK signal 816 to an ASK signal, with reference tothe flowchart 1419 and to the timing diagrams of FIGS. 41A–E. In step1420, the under-sampling module 1606 receives the FSK signal 816 (FIG.41A). In step 1422, the under-sampling module 1606 receives theunder-sampling signal 4107 (FIG. 41C). In step 1424, the under-samplingmodule 1606 under-samples the FSK signal 816 at the aliasing of theunder-sampling signal 4107 to down-convert the FSK signal 816 to the ASKsignal 4112 of FIG. 41D or the ASK signal 4114 in FIG. 41E.

-   -   -   3.2.3 Other Example Embodiments

The embodiments described above are provided for purposes ofillustration. These embodiments are not intended to limit the invention.Alternate embodiments, differing slightly or substantially from thosedescribed herein, will be apparent to persons skilled in the relevantart(s) based on the teachings contained herein. Such alternateembodiments fall within the scope and spirit of the present invention.

-   -   3.3 Implementation Examples

Exemplary operational and/or structural implementations related to themethod(s), structure(s), and/or embodiments described above arepresented in Sections 4 and 5 below. These implementations are presentedfor purposes of illustration, and not limitation. The invention is notlimited to the particular implementation examples described therein.Alternate implementations (including equivalents, extensions,variations, deviations, etc., of those described herein) will beapparent to persons skilled in the relevant art(s) based on theteachings contained herein. Such alternate implementations fall withinthe scope and spirit of the present invention.

4. Implementation Examples

Exemplary operational and/or structural implementations related to themethod(s), structure(s), and/or embodiments described in theSub-Sections above are presented in this section (and its subsections).These implementations are presented herein for purposes of illustration,and not limitation. The invention is not limited to the particularimplementation examples described herein. Alternate implementations(including equivalents, extensions, variations, deviations, etc., ofthose described herein) will be apparent to persons skilled in therelevant art(s) based on the teachings contained herein. Such alternateimplementations fall within the scope and spirit of the presentinvention.

FIG. 13 illustrates a generic aliasing system 1302, including analiasing module 1306. FIG. 16 illustrates an under-sampling system 1602,which includes an under-sampling module 1606. The under-sampling module1606 receives an under-sampling signal 1604 having an aliasing rateF_(AR). The under-sampling signal 1604 includes a train of pulses havingnegligible apertures that tend towards zero time in duration. The pulsesrepeat at the aliasing rate F_(AR). The under-sampling system 1602 is anexample implementation of the generic aliasing system 1303. Theunder-sampling system 1602 outputs a down-converted signal 1308A.

FIG. 26A illustrates an exemplary sample and hold system 2602, which isan exemplary implementation of the under-sampling system 1602. Thesample and hold system 2602 is described below.

FIG. 26B illustrates an exemplary inverted sample and hold system 2606,which is an alternative example implementation of the under-samplingsystem 1602. The inverted sample and hold system 2606 is describedbelow.

-   -   4.1 The Under-Sampling System as a Sample and Hold System

FIG. 26A is a block diagram of a the sample and hold system 2602, whichis an example embodiment of the under-sampling module 1606 in FIG. 16,which is an example embodiment of the generic aliasing module 1306 inFIG. 13.

The sample and hold system 2602 includes a sample and hold module 2604,which receives the EM signal 1304 and the under-sampling signal 1604.The sample and hold module 2604 under-samples the EM signal at thealiasing rate of the under-sampling signal 1604, as described in thesections above with respect to the flowcharts 1401 in FIG. 14A, 1407 inFIG. 14B, 1413 in FIG. 14C and 1419 in FIG. 14D. The under-samplingsystem 1602 outputs a down-converted signal 1308A.

FIG. 27 illustrates an under-sampling system 2701 as a sample and holdsystem, which is an example implementation of the under-sampling system2602. The under-sampling system 2701 includes a switch module 2702 and aholding module 2706. The under-sampling system 2701 is described below.

FIG. 24A illustrates an under-sampling system 2401 as a break beforemake under-sampling system, which is an alternative implementation ofthe under-sampling system 2602. The break before make under-samplingsystem 2401 is described below.

-   -   -   4.1.1 The Sample and Hold System as a Switch Module and a            Holding Module

FIG. 27 illustrates an exemplary embodiment of the sample and holdmodule 2604 from FIG. 26A. In the exemplary embodiment, the sample andhold module 2604 includes a switch module 2702, and a holding module2706.

Preferably, the switch module 2702 and the holding module 2706under-sample the EM signal 1304 to down-convert it in any of the mannersshown in the operation flowcharts 1401, 1407, 1413 and 1419. Forexample, the sample and hold module 2604 can receive and under-sampleany of the modulated carrier signal signals described above, including,but not limited to, the analog AM signal 516, the digital AM signal 616,the analog FM signal 716, the digital FM signal 816, the analog PMsignal 916, the digital PM signal 1016, etc., and any combinationsthereof.

The switch module 2702 and the holding module 2706 down-convert the EMsignal 1304 to an intermediate signal, to a demodulated baseband or to adifferent modulation scheme, depending upon the aliasing rate.

For example, operation of the switch module 2702 and the holding module2706 are now described for down-converting the EM signal 1304 to anintermediate signal, with reference to the flowchart 1407 and theexample timing diagrams in FIG. 79A–F.

In step 1408, the switch module 2702 receives the EM signal 1304 (FIG.79A). In step 1410, the switch module 2702 receives the under-samplingsignal 1604 (FIG. 79C). In step 1412, the switch module 2702 and theholding module 2706 cooperate to under-sample the EM signal 1304 anddown-convert it to an intermediate signal. More specifically, duringstep 1412, the switch module 2702 closes during each under-samplingpulse to couple the EM signal 1304 to the holding module 2706. In anembodiment, the switch module 2702 closes on rising edges of the pulses.In an alternative embodiment, the switch module 2702 closes on fallingedges of the pulses. When the EM signal 1304 is coupled to the holdingmodule 2706, the amplitude of the EM signal 1304 is captured by theholding module 2706. The holding module 2706 is designed to capture andhold the amplitude of the EM signal 1304 within the short time frame ofeach negligible aperture pulse. FIG. 79B illustrates the EM signal 1304after under-sampling.

The holding module 2706 substantially holds or maintains eachunder-sampled amplitude until a subsequent under-sample. (FIG. 79D). Theholding module 2706 outputs the under-sampled amplitudes as thedown-converted signal 1308A. The holding module 2706 can output thedown-converted signal 1308A as an unfiltered signal, such as a stairstep signal (FIG. 79E), as a filtered down-converted signal (FIG. 79F)or as a partially filtered down-converted signal.

-   -   -   4.1.2 The Sample and Hold System as Break-Before-Make Module

FIG. 24A illustrates a break-before-make under-sampling system 2401,which is an alternative implementation of the under-sampling system2602.

Preferably, the break-before-make under-sampling system 2401under-samples the EM signal 1304 to down-convert it in any of themanners shown in the operation flowcharts 1401, 1407, 1413 and 1419. Forexample, the sample and hold module 2604 can receive and under-sampleany of the unmodulated or modulated carrier signal signals describedabove, including, but not limited to, the analog AM signal 516, thedigital AM signal 616, the analog FM signal 716, the digital FM signal816, the analog PM signal 916, the digital PM signal 1016, etc., andcombinations thereof.

The break-before-make under-sampling system 2401 down-converts the EMsignal 1304 to an intermediate signal, to a demodulated baseband or to adifferent modulation scheme, depending upon the aliasing rate.

FIG. 24A includes a break-before-make switch 2402. The break-before-makeswitch 2402 includes a normally open switch 2404 and a normally closedswitch 2406. The normally open switch 2404 is controlled by theunder-sampling signal 1604, as previously described. The normally closedswitch 2406 is controlled by an isolation signal 2412. In an embodiment,the isolation signal 2412 is generated from the under-sampling signal1604. Alternatively, the under-sampling signal 1604 is generated fromthe isolation signal 2412. Alternatively, the isolation signal 2412 isgenerated independently from the under-sampling signal 1604. Thebreak-before-make module 2402 substantially isolates a sample and holdinput 2408 from a sample and hold output 2410.

FIG. 24B illustrates an example timing diagram of the under-samplingsignal 1604 that controls the normally open switch 2404. FIG. 24Cillustrates an example timing diagram of the isolation signal 2412 thatcontrols the normally closed switch 2406. Operation of thebreak-before-make module 2402 is described with reference to the exampletiming diagrams in FIGS. 24B and 24C.

Prior to time t0, the normally open switch 2404 and the normally closedswitch 2406 are at their normal states.

At time t0, the isolation signal 2412 in FIG. 24C opens the normallyclosed switch 2406. Then, just after time t0, the normally open switch2404 and the normally closed switch 2406 are open and the input 2408 isisolated from the output 2410.

At time t1, the under-sampling signal 1604 in FIG. 24B briefly closesthe normally open switch 2404. This couples the EM signal 1304 to theholding module 2416.

Prior to t2, the under-sampling signal 1604 in FIG. 24B opens thenormally open switch 2404. This de-couples the EM signal 1304 from theholding module 2416.

At time t2, the isolation signal 2412 in FIG. 24C closes the normallyclosed switch 2406. This couples the holding module 2416 to the output2410.

The break-before-make under-sampling system 2401 includes a holdingmodule 2416, which can be similar to the holding module 2706 in FIG. 27.The break-before-make under-sampling system 2401 down-converts the EMsignal 1304 in a manner similar to that described with reference to theunder-sampling system 2702 in FIG. 27.

-   -   -   4.1.3 Example Implementations of the Switch Module

The switch module 2702 in FIG. 27 and the switch modules 2404 and 2406in FIG. 24A can be any type of switch device that preferably has arelatively low impedance when closed and a relatively high impedancewhen open. The switch modules 2702, 2404 and 2406 can be implementedwith normally open or normally closed switches. The switch device neednot be an ideal switch device. FIG. 28B illustrates the switch modules2702, 2404 and 2406 as, for example, a switch module 2810.

The switch device 2810 (e.g., switch modules 2702, 2404 and 2406) can beimplemented with any type of suitable switch device, including, but notlimited to mechanical switch devices and electrical switch devices,optical switch devices, etc., and combinations thereof. Such devicesinclude, but are not limited to transistor switch devices, diode switchdevices, relay switch devices, optical switch devices, micro-machineswitch devices, etc.

In an embodiment, the switch module 2810 can be implemented as atransistor, such as, for example, a field effect transistor (FET), abi-polar transistor, or any other suitable circuit switching device.

In FIG. 28A, the switch module 2810 is illustrated as a FET 2802. TheFET 2802 can be any type of FET, including, but not limited to, aMOSFET, a JFET, a GaAsFET, etc. The FET 2802 includes a gate 2804, asource 2806 and a drain 2808. The gate 2804 receives the under-samplingsignal 1604 to control the switching action between the source 2806 andthe drain 2808. Generally, the source 2806 and the drain 2808 areinterchangeable.

It should be understood that the illustration of the switch module 2810as a FET 2802 in FIG. 28A is for example purposes only. Any devicehaving switching capabilities could be used to implement the switchmodule 2810 (e.g., switch modules 2702, 2404 and 2406), as will beapparent to persons skilled in the relevant art(s) based on thediscussion contained herein.

In FIG. 28C, the switch module 2810 is illustrated as a diode switch2812, which operates as a two lead device when the under-sampling signal1604 is coupled to the output 2813.

In FIG. 28D, the switch module 2810 is illustrated as a diode switch2814, which operates as a two lead device when the under-sampling signal1604 is coupled to the output 2815.

-   -   -   4.1.4 Example Implementations of the Holding Module

The holding modules 2706 and 2416 preferably captures and holds theamplitude of the original, unaffected, EM signal 1304 within the shorttime frame of each negligible aperture under-sampling signal pulse.

In an exemplary embodiment, holding modules 2706 and 2416 areimplemented as a reactive holding module 2901 in FIG. 29A, although theinvention is not limited to this embodiment. A reactive holding moduleis a holding module that employs one or more reactive electricalcomponents to preferably quickly charge to the amplitude of the EMsignal 1304. Reactive electrical components include, but are not limitedto, capacitors and inductors.

In an embodiment, the holding modules 2706 and 2416 include one or morecapacitive holding elements, illustrated in FIG. 29B as a capacitiveholding module 2902. In FIG. 29C, the capacitive holding module 2902 isillustrated as one or more capacitors illustrated generally ascapacitor(s) 2904. Recall that the preferred goal of the holding modules2706 and 2416 is to quickly charge to the amplitude of the EM signal1304. In accordance with principles of capacitors, as the negligibleaperture of the under-sampling pulses tends to zero time in duration,the capacitive value of the capacitor 2904 can tend towards zero Farads.Example values for the capacitor 2904 can range from tens of pico Faradsto fractions of pico Farads. A terminal 2906 serves as an output of thesample and hold module 2604. The capacitive holding module 2902 providesthe under-samples at the terminal 2906, where they can be measured as avoltage. FIG. 29F illustrates the capacitive holding module 2902 asincluding a series capacitor 2912, which can be utilized in an invertedsample and hold system as described below.

In an alternative embodiment, the holding modules 2706 and 2416 includeone or more inductive holding elements, illustrated in FIG. 29D as aninductive holding module 2908.

In an alternative embodiment, the holding modules 2706 and 2416 includea combination of one or more capacitive holding elements and one or moreinductive holding elements, illustrated in FIG. 29E as acapacitive/inductive holding module 2910.

FIG. 29G illustrates an integrated under-sampling system that can beimplemented to down-convert the EM signal 1304 as illustrated in, anddescribed with reference to, FIGS. 79A–F.

-   -   -   4.1.5 Optional Under-Sampling Signal Module

FIG. 30 illustrates an under-sampling system 3001, which is an exampleembodiment of the under-sampling system 1602. The under-sampling system3001 includes an optional under-sampling signal module 3002 that canperform any of a variety of functions or combinations of functions,including, but not limited to, generating the under-sampling signal1604.

In an embodiment, the optional under-sampling signal module 3002includes an aperture generator, an example of which is illustrated inFIG. 29J as an aperture generator 2920. The aperture generator 2920generates negligible aperture pulses 2926 from an input signal 2924. Theinput signal 2924 can be any type of periodic signal, including, but notlimited to, a sinusoid, a square wave, a saw-tooth wave, etc. Systemsfor generating the input signal 2924 are described below.

The width or aperture of the pulses 2926 is determined by delay throughthe branch 2922 of the aperture generator 2920. Generally, as thedesired pulse width decreases, the tolerance requirements of theaperture generator 2920 increase. In other words, to generate negligibleaperture pulses for a given input EM frequency, the components utilizedin the example aperture generator 2920 require greater reaction times,which are typically obtained with more expensive elements, such asgallium arsenide (GaAs), etc.

The example logic and implementation shown in the aperture generator2920 are provided for illustrative purposes only, and are not limiting.The actual logic employed can take many forms. The example aperturegenerator 2920 includes an optional inverter 2928, which is shown forpolarity consistency with other examples provided herein. An exampleimplementation of the aperture generator 2920 is illustrated in FIG.29K.

Additional examples of aperture generation logic is provided in FIGS.29H and 29I. FIG. 29H illustrates a rising edge pulse generator 2940,which generates pulses 2926 on rising edges of the input signal 2924.FIG. 291 illustrates a falling edge pulse generator 2950, whichgenerates pulses 2926 on falling edges of the input signal 2924.

In an embodiment, the input signal 2924 is generated externally of theunder-sampling signal module 3002, as illustrated in FIG. 30.Alternatively, the input signal 2924 is generated internally by theunder-sampling signal module 3002. The input signal 2924 can begenerated by an oscillator, as illustrated in FIG. 29L by an oscillator2930. The oscillator 2930 can be internal to the under-sampling signalmodule 3002 or external to the under-sampling signal module 3002. Theoscillator 2930 can be external to the under-sampling system 3001.

The type of down-conversion performed by the under-sampling system 3001depends upon the aliasing rate of the under-sampling signal 1604, whichis determined by the frequency of the pulses 2926. The frequency of thepulses 2926 is determined by the frequency of the input signal 2924. Forexample, when the frequency of the input signal 2924 is substantiallyequal to a harmonic or a sub-harmonic of the EM signal 1304, the EMsignal 1304 is directly down-converted to baseband (e.g. when the EMsignal is an AM signal or a PM signal), or converted from FM to a non-FMsignal. When the frequency of the input signal 2924 is substantiallyequal to a harmonic or a sub-harmonic of a difference frequency, the EMsignal 1304 is down-converted to an intermediate signal.

The optional under-sampling signal module 3002 can be implemented inhardware, software, firmware, or any combination thereof.

-   -   4.2 The Under-Sampling System as an Inverted Sample and Hold

FIG. 26B illustrates an exemplary inverted sample and hold system 2606,which is an alternative example implementation of the under-samplingsystem 1602.

FIG. 42 illustrates a inverted sample and hold system 4201, which is anexample implementation of the inverted sample and hold system 2606 inFIG. 26B. The sample and hold system 4201 includes a sample and holdmodule 4202, which includes a switch module 4204 and a holding module4206. The switch module 4204 can be implemented as described above withreference to FIGS. 28A–D.

The holding module 4206 can be implemented as described above withreference to FIGS. 29A–F, for the holding modules 2706 and 2416. In theillustrated embodiment, the holding module 4206 includes one or morecapacitors 4208. The capacitor(s) 4208 are selected to pass higherfrequency components of the EM signal 1304 through to a terminal 4210,regardless of the state of the switch module 4204. The capacitor(s) 4208stores charge from the EM signal 1304 during aliasing pulses of theunder-sampling signal 1604 and the signal at the terminal 4210 isthereafter off-set by an amount related to the charge stored in thecapacitor(s) 4208.

Operation of the inverted sample and hold system 4201 is illustrated inFIGS. 34A–F. FIG. 34A illustrates an example EM signal 1304. FIG. 34Billustrates the EM signal 1304 after under-sampling. FIG. 34Cillustrates the under-sampling signal 1606, which includes a train ofaliasing pulses having negligible apertures.

FIG. 34D illustrates an example down-converted signal 1308A. FIG. 34Eillustrates the down-converted signal 1308A on a compressed time scale.Since the holding module 4206 is series element, the higher frequencies(e.g., RF) of the EM signal 1304 can be seen on the down-convertedsignal. This can be filtered as illustrated in FIG. 34F.

The inverted sample and hold system 4201 can be used to down-convert anytype of EM signal, including modulated carrier signals and unmodulatedcarrier signals, to IF signals and to demodulated baseband signals.

-   -   4.3 Other Implementations

The implementations described above are provided for purposes ofillustration. These implementations are not intended to limit theinvention. Alternate implementations, differing slightly orsubstantially from those described herein, will be apparent to personsskilled in the relevant art(s) based on the teachings contained herein.Such alternate implementations fall within the scope and spirit of thepresent invention.

5. Optional Optimizations of Under-Sampling at an Aliasing Rate

The methods and systems described in sections above can be optionallyoptimized with one or more of the optimization methods or systemsdescribed below.

-   -   5.1 Doubling the Aliasing Rate (F_(AR)) of the Under-Sampling        Signal

In an embodiment, the optional under-sampling signal module 3002 in FIG.30 includes a pulse generator module that generates aliasing pulses at amultiple of the frequency of the oscillating source, such as twice thefrequency of the oscillating source. The input signal 2926 may be anysuitable oscillating source.

FIG. 31 illustrates an example circuit 3102 that generates a doubleroutput signal 3104 (FIGS. 31 and 43B) that may be used as anunder-sampling signal 1604. The example circuit 3102 generates pulses onrising and falling edges of the input oscillating signal 3106 of FIG.43A. Input oscillating signal 3106 is one embodiment of optional inputsignal 2926. The circuit 3102 can be implemented as a pulse generatorand aliasing rate (F_(AR)) doubler, providing the under-sampling signal1604 to under-sampling module 1606 in FIG. 30.

The aliasing rate is twice the frequency of the input oscillating signalF_(OSC) 3106, as shown by EQ. (9) below.F _(AR)=2·F _(OSC)  EQ. (9)

The aperture width of the aliasing pulses is determined by the delaythrough a first inverter 3108 of FIG. 31. As the delay is increased, theaperture is increased. A second inverter 3112 is shown to maintainpolarity consistency with examples described elsewhere. In an alternateembodiment inverter 3112 is omitted. Preferably, the pulses havenegligible aperture widths that tend toward zero time. The doubleroutput signal 3104 may be further conditioned as appropriate to drive aswitch module with negligible aperture pulses. The circuit 3102 may beimplemented with integrated circuitry, discretely, with equivalent logiccircuitry, or with any valid fabrication technology.

-   -   5.2 Differential Implementations

The invention can be implemented in a variety of differentialconfigurations. Differential configurations are useful for reducingcommon mode noise. This can be very useful in receiver systems wherecommon mode interference can be caused by intentional or unintentionalradiators such as cellular phones, CB radios, electrical appliances etc.Differential configurations are also useful in reducing any common modenoise due to charge injection of the switch in the switch module or dueto the design and layout of the system in which the invention is used.Any spurious signal that is induced in equal magnitude and equal phasein both input leads of the invention will be substantially reduced oreliminated. Some differential configurations, including some of theconfigurations below, are also useful for increasing the voltage and/orfor increasing the power of the down-converted signal 1308A. While anexample of a differential under-sampling module is shown below, theexample is shown for the purpose of illustration, not limitation.Alternate embodiments (including equivalents, extensions, variations,deviations, etc.) of the embodiment described herein will be apparent tothose skilled in the relevant art based on the teachings containedherein. The invention is intended and adapted to include such alternateembodiments.

FIG. 44A illustrates an example differential system 4402 that can beincluded in the under-sampling module 1606. The differential system 4202includes an inverted under-sampling design similar to that describedwith reference to FIG. 42. The differential system 4402 includes inputs4404 and 4406 and outputs 4408 and 4410. The differential system 4402includes a first inverted sample and hold module 4412, which includes aholding module 4414 and a switch module 4416. The differential system4402 also includes a second inverted sample and hold module 4418, whichincludes a holding module 4420 and the switch module 4416, which itshares in common with sample and hold module 4412.

One or both of the inputs 4404 and 4406 are coupled to an EM signalsource. For example, the inputs can be coupled to an EM signal source,wherein the input voltages at the inputs 4404 and 4406 are substantiallyequal in amplitude but 180 degrees out of phase with one another.Alternatively, where dual inputs are unavailable, one of the inputs 4404and 4406 can be coupled to ground.

In operation, when the switch module 4416 is closed, the holding modules4414 and 4420 are in series and, provided they have similar capacitivevalues, they charge to equal amplitudes but opposite polarities. Whenthe switch module 4416 is open, the voltage at the output 4408 isrelative to the input 4404, and the voltage at the output 4410 isrelative to the voltage at the input 4406.

Portions of the voltages at the outputs 4408 and 4410 include voltageresulting from charge stored in the holding modules 4414 and 4420,respectively, when the switch module 4416 was closed. The portions ofthe voltages at the outputs 4408 and 4410 resulting from the storedcharge are generally equal in amplitude to one another but 180 degreesout of phase.

Portions of the voltages at the outputs 4408 and 4410 also includeripple voltage or noise resulting from the switching action of theswitch module 4416. But because the switch module is positioned betweenthe two outputs, the noise introduced by the switch module appears atthe outputs 4408 and 4410 as substantially equal and in-phase with oneanother. As a result, the ripple voltage can be substantially filteredout by inverting the voltage at one of the outputs 4408 or 4410 andadding it to the other remaining output. Additionally, any noise that isimpressed with substantially equal amplitude and equal phase onto theinput terminals 4404 and 4406 by any other noise sources will tend to becanceled in the same way.

The differential system 4402 is effective when used with a differentialfront end (inputs) and a differential back end (outputs). It can also beutilized in the following configurations, for example:

-   -   a) A single-input front end and a differential back end; and    -   b) A differential front end and single-output back end.        Examples of these system are provided below.        -   5.2.1 Differential Input-to-Differential Output

FIG. 44B illustrates the differential system 4402 wherein the inputs4404 and 4406 are coupled to equal and opposite EM signal sources,illustrated here as dipole antennas 4424 and 4426. In this embodiment,when one of the outputs 4408 or 4410 is inverted and added to the otheroutput, the common mode noise due to the switching module 4416 and othercommon mode noise present at the input terminals 4404 and 4406 tend tosubstantially cancel out.

-   -   -   5.2.2 Single Input-to-Differential Output

FIG. 44C illustrates the differential system 4402 wherein the input 4404is coupled to an EM signal source such as a monopole antenna 4428 andthe input 4406 is coupled to ground.

FIG. 44E illustrates an example single input to differential outputreceiver/down-converter system 4436. The system 4436 includes thedifferential system 4402 wherein the input 4406 is coupled to ground.The input 4404 is coupled to an EM signal source 4438.

The outputs 4408 and 4410 are coupled to a differential circuit 4444such as a filter, which preferably inverts one of the outputs 4408 or4410 and adds it to the other output 4408 or 4410. This substantiallycancels common mode noise generated by the switch module 4416. Thedifferential circuit 4444 preferably filters the higher frequencycomponents of the EM signal 1304 that pass through the holding modules4414 and 4420. The resultant filtered signal is output as thedown-converted signal 1308A.

-   -   -   5.2.3 Differential Input-to-Single Output

FIG. 44D illustrates the differential system 4402 wherein the inputs4404 and 4406 are coupled to equal and opposite EM signal sourcesillustrated here as dipole antennas 4430 and 4432. The output is takenfrom terminal 4408.

-   -   5.3 Smoothing the Down-Converted Signal

The down-converted signal 1308A may be smoothed by filtering as desired.The differential circuit 4444 implemented as a filter in FIG. 44Eillustrates but one example. Filtering may be accomplished in any of thedescribed embodiments by hardware, firmware and software implementationas is well known by those skilled in the arts.

-   -   5.4 Load Impedance and Input/Output Buffering

Some of the characteristics of the down-converted signal 1308A dependupon characteristics of a load placed on the down-converted signal1308A. For example, in an embodiment, when the down-converted signal1308A is coupled to a high impedance load, the charge that is applied toa holding module such as holding module 2706 in FIG. 27 or 2416 in FIG.24A during a pulse generally remains held by the holding module untilthe next pulse. This results in a substantially stair-step-likerepresentation of the down-converted signal 1308A as illustrated in FIG.15C, for example. A high impedance load enables the under-samplingsystem 1606 to accurately represent the voltage of the originalunaffected input signal.

The down-converted signal 1308A can be buffered with a high impedanceamplifier, if desired.

Alternatively, or in addition to buffering the down-converted signal1308A, the input EM signal may be buffered or amplified by a low noiseamplifier.

-   -   5.5 Modifying the Under-Sampling Signal Utilizing Feedback

FIG. 30 shows an embodiment of a system 3001 which uses down-convertedsignal 1308A as feedback 3006 to control various characteristics of theunder-sampling module 1606 to modify the down-converted signal 1308A.

Generally, the amplitude of the down-converted signal 1308A varies as afunction of the frequency and phase differences between the EM signal1304 and the under-sampling signal 1604. In an embodiment, thedown-converted signal 1308A is used as the feedback 3006 to control thefrequency and phase relationship between the EM signal 1304 and theunder-sampling signal 1604. This can be accomplished using the exampleblock diagram shown in FIG. 32A. The example circuit illustrated in FIG.32A can be included in the under-sampling signal module 3002. Alternateimplementations will be apparent to persons skilled in the relevantart(s) based on the teachings contained herein. Alternateimplementations fall within the scope and spirit of the presentinvention. In this embodiment a state-machine is used for clarity, andis not limiting.

In the example of FIG. 32A, a state machine 3204 reads an analog todigital converter, A/D 3202, and controls a digital to analog converter(DAC) 3206. In an embodiment, the state machine 3204 includes 2 memorylocations, Previous and Current, to store and recall the results ofreading A/D 3202. In an embodiment, the state machine 3204 utilizes atleast one memory flag.

DAC 3206 controls an input to a voltage controlled oscillator, VCO 3208.VCO 3208 controls a frequency input of a pulse generator 3210, which, inan embodiment, is substantially similar to the pulse generator shown inFIG. 29J. The pulse generator 3210 generates the under-sampling signal1604.

In an embodiment, the state machine 3204 operates in accordance with thestate machine flowchart 3220 in FIG. 32B. The result of this operationis to modify the frequency and phase relationship between theunder-sampling signal 1604 and the EM signal 1304, to substantiallymaintain the amplitude of the down-converted signal 1308A at an optimumlevel.

The amplitude of the down-converted signal 1308A can be made to varywith the amplitude of the under-sampling signal 1604. In an embodimentwhere Switch Module 2702 is a FET as shown in FIG. 28A, wherein the gate2804 receives the under-sampling signal 1604, the amplitude of theunder-sampling signal 1604 can determine the “on” resistance of the FET,which affects the amplitude of down-converted signal 1308A.Under-sampling signal module 3002, as shown in FIG. 32C, can be ananalog circuit that enables an automatic gain control function.Alternate implementations will be apparent to persons skilled in therelevant art(s) based on the teachings contained herein. Alternateimplementations fall within the scope and spirit of the presentinvention.

III. Down-Converting by Transferring Energy

The energy transfer embodiments of the invention provide enhanced signalto noise ratios and sensitivity to very small signals, as well aspermitting the down-converted signal to drive lower impedance loadsunassisted. The energy transfer aspects of the invention are representedgenerally by 4506 in FIGS. 45A and 45B. Fundamental descriptions of howthis is accomplished is presented step by step beginning with acomparison with an under-sampling system.

1. Energy Transfer Compared to Under-Sampling

Section II above disclosed methods and systems for down-converting an EMsignal by under-sampling. The under-sampling systems utilize a sampleand hold system controlled by an under-sampling signal. Theunder-sampling signal includes a train of pulses having negligibleapertures that tend towards zero time in duration. The negligibleaperture pulses minimize the amount of energy transferred from the EMsignal. This protects the under-sampled EM signal from distortion ordestruction. The negligible aperture pulses also make the sample andhold system a high impedance system. An advantage of under-sampling isthat the high impedance input allows accurate voltage reproduction ofthe under-sampled EM signal. The methods and systems disclosed inSection II are thus useful for many situations including, but notlimited to, monitoring EM signals without distorting or destroying them.

Because the under-sampling systems disclosed in Section II transfer onlynegligible amounts of energy, they are not suitable for all situations.For example, in radio communications, received radio frequency (RF)signals are typically very weak and must be amplified in order todistinguish them over noise. The negligible amounts of energytransferred by the under-sampling systems disclosed in Section II maynot be sufficient to distinguish received RF signals over noise.

In accordance with an aspect of the invention, methods and systems aredisclosed below for down-converting EM signals by transferringnon-negligible amounts of energy from the EM signals. The resultantdown-converted signals have sufficient energy to allow thedown-converted signals to be distinguishable from noise. The resultantdown-converted signals also have sufficient energy to drive lowerimpedance circuits without buffering.

Down-converting by transferring energy is introduced below in anincremental fashion to distinguish it from under-sampling. Theintroduction begins with further descriptions of under-sampling.

-   -   1.1 Review of Under-Sampling

FIG. 78A illustrates an exemplary under-sampling system 7802 fordown-converting an input EM signal 7804. The under-sampling system 7802includes a switching module 7806 and a holding module shown as a holdingcapacitance 7808. An under-sampling signal 7810 controls the switchmodule 7806. The under-sampling signal 7810 includes a train of pulseshaving negligible pulse widths that tend toward zero time. An example ofa negligible pulse width or duration can be in the range of 1–10 psecfor under-sampling a 900 MHZ signal. Any other suitable negligible pulseduration can be used as well, where accurate reproduction of theoriginal unaffected input signal voltage is desired withoutsubstantially affecting the original input signal voltage.

In an under-sampling environment, the holding capacitance 7808preferably has a small capacitance value. This allows the holdingcapacitance 7808 to substantially charge to the voltage of the input EMsignal 7804 during the negligible apertures of the under-sampling signalpulses. For example, in an embodiment, the holding capacitance 7808 hasa value in the range of 1 pF. Other suitable capacitance values can beused to achieve substantially the voltage of the original unaffectedinput signal. Various capacitances can be employed for certain effects,which are described below. The under-sampling system is coupled to aload 7812. In FIG. 78B, the load 7812 of FIG. 78A is illustrated as ahigh impedance load 7818. A high impedance load is one that isrelatively insignificant to an output drive impedance of the system fora given output frequency. The high impedance load 7818 allows theholding capacitance 7808 to substantially maintain the chargeaccumulated during the under-sampling pulses.

FIGS. 79A–F illustrate example timing diagrams for the under-samplingsystem 7802. FIG. 79A illustrates an example input EM signal 7804.

FIG. 79C illustrates an example under-sampling signal 7810, includingpulses 7904 having negligible apertures that tend towards zero time induration.

FIG. 79B illustrates the negligible effects to the input EM signal 7804when under-sampled, as measured at a terminal 7814 of the under-samplingsystem 7802. In FIG. 79B, negligible distortions 7902 correlate with thepulses of the under-sampling signal 7810. In this embodiment, thenegligible distortions 7902 occur at different locations of subsequentcycles of the input EM signal 7804. As a result, the input EM signalwill be down-converted. The negligible distortions 7902 representnegligible amounts of energy, in the form of charge that is transferredto the holding capacitance 7808.

When the load 7812 is a high impedance load, the holding capacitance7808 does not significantly discharge between pulses 7904. As a result,charge that is transferred to the holding capacitance 7808 during apulse 7904 tends to “hold” the voltage value sampled constant at theterminal 7816 until the next pulse 7904. When voltage of the input EMsignal 7804 changes between pulses 7904, the holding capacitance 7808substantially attains the new voltage and the resultant voltage at theterminal 7816 forms a stair step pattern, as illustrated in FIG. 79D.

FIG. 79E illustrates the stair step voltage of FIG. 79D on a compressedtime scale. The stair step voltage illustrated in FIG. 79E can befiltered to produce the signal illustrated in FIG. 79F. The signalsillustrated in FIGS. 79D, E, and F have substantially all of thebaseband characteristics of the input EM signal 7804 in FIG. 79A, exceptthat the signals illustrated in FIGS. 79D, E, and F have beensuccessfully down-converted.

Note that the voltage level of the down-converted signals illustrated inFIGS. 79E and 79F are substantially close to the voltage level of theinput EM signal 7804. The under-sampling system 7802 thus down-convertsthe input EM signal 7804 with reasonable voltage reproduction, withoutsubstantially affecting the input EM signal 7804. But also note that thepower available at the output is relatively negligible (e.g.:V²/R; ˜5 mVand 1 MOhm), given the input EM signal 7804 would typically have adriving impedance, in an RF environment, of 50 Ohms (e.g.: V²/R; ˜5 mVand 50 Ohms).

-   -   -   1.1.1 Effects of Lowering the Impedance of the Load

Effects of lowering the impedance of the load 7812 are now described.FIGS. 80A–E illustrate example timing diagrams for the under-samplingsystem 7802 when the load 7812 is a relatively low impedance load, onethat is significant relative to the output drive impedance of the systemfor a given output frequency.

FIG. 80A illustrates an example input EM signal 7804, which issubstantially similar to that illustrated in FIG. 79A.

FIG. 80C illustrates an example under-sampling signal 7810, includingpulses 8004 having negligible apertures that tend towards zero time induration. The example under-sampling signal 7810 illustrated in FIG. 80Cis substantially similar to that illustrated in FIGS. 79C.

FIG. 80B illustrates the negligible effects to the input EM signal 7804when under-sampled, as measured at a terminal 7814 of the under-samplingsystem 7802. In FIG. 80B, negligible distortions 8002 correlate with thepulses 8004 of the under-sampling signal 7810 in FIG. 80C. In thisexample, the negligible distortions 8002 occur at different locations ofsubsequent cycles of the input EM signal 7804. As a result, the input EMsignal 7804 will be down-converted. The negligible distortions 8002represent negligible amounts of energy, in the form of charge that istransferred to the holding capacitance 7808.

When the load 7812 is a low impedance load, the holding capacitance 7808is significantly discharged by the load between pulses 8004 (FIG. 80C).As a result, the holding capacitance 7808 cannot reasonably attain or“hold” the voltage of the original EM input signal 7804, as was seen inthe case of FIG. 79D. Instead, the charge appears as the outputillustrated in FIG. 80D.

FIG. 80E illustrates the output from FIG. 80D on a compressed timescale. The output in FIG. 80E can be filtered to produce the signalillustrated in FIG. 80F. The down-converted signal illustrated in FIG.80F is substantially similar to the down-converted signal illustrated inFIG. 79F, except that the signal illustrated in FIG. 80F issubstantially smaller in magnitude than the amplitude of thedown-converted signal illustrated in FIG. 79F. This is because the lowimpedance of the load 7812 prevents the holding capacitance 7808 fromreasonably attaining or “holding” the voltage of the original EM inputsignal 7804. As a result, the down-converted signal illustrated in FIG.80F cannot provide optimal voltage reproduction, and has relativelynegligible power available at the output (e.g.: V²/R; ˜200 μV and 2KOhms), given the input EM signal 7804 would typically have a drivingimpedance, in an RF environment, of 50 Ohms (e.g.: V²/R; ˜5 mV and 50Ohms).

-   -   -   1.1.2 Effects of Increasing the Value of the Holding            Capacitance

Effects of increasing the value of the holding capacitance 7808, whilehaving to drive a low impedance load 7812, is now described. FIGS. 81A–Fillustrate example timing diagrams for the under-sampling system 7802when the holding capacitance 7808 has a larger value, in the range of 18pF for example.

FIG. 81 A illustrates an example input EM signal 7804, which issubstantially similar to that illustrated in FIGS. 79A and 80A.

FIG. 81C illustrates an example under-sampling signal 7810, includingpulses 8104 having negligible apertures that tend towards zero time induration. The example under-sampling signal 7810 illustrated in FIG. 81Cis substantially similar to that illustrated in FIGS. 79C and 80C.

FIG. 81B illustrates the negligible effects to the input EM signal 7804when under-sampled, as measured at a terminal 7814 of the under-samplingsystem 7802. In FIG. 81B, negligible distortions 8102 correlate with thepulses 8104 of the under-sampling signal 7810 in FIG. 81C. Upon closeinspection, the negligible distortions 8102 occur at different locationsof subsequent cycles of the input EM signal 7804. As a result, the inputEM signal 7804 will be down-converted. The negligible distortions 8102represent negligible amounts of energy, in the form of charge that istransferred to the holding capacitance 7808.

FIG. 81D illustrates the voltage measured at the terminal 7816, which isa result of the holding capacitance 7808 attempting to attain and “hold”the original input EM signal voltage, but failing to do so, during thenegligible apertures of the pulses 8104 illustrated in FIG. 81C.

Recall that when the load 7812 is a low impedance load, the holdingcapacitance 7808 is significantly discharged by the load between pulses8104 (FIG. 81C), this again is seen in FIGS. 81D and E. As a result, theholding capacitance 7808 cannot reasonably attain or “hold” the voltageof the original EM input signal 7804, as was seen in the case of FIG.79D. Instead, the charge appears as the output illustrated in FIG. 81D.

FIG. 81E illustrates the down-converted signal 8106 on a compressed timescale. Note that the amplitude of the down-converted signal 8106 issignificantly less than the amplitude of the down-converted signalillustrated in FIGS. 80D and 80E. This is due to the higher capacitivevalue of the holding capacitance 7808. Generally, as the capacitivevalue increases, it requires more charge to increase the voltage for agiven aperture. Because of the negligible aperture of the pulses 8104 inFIG. 81C, there is insufficient time to transfer significant amounts ofenergy or charge from the input EM signal 7804 to the holdingcapacitance 7808. As a result, the amplitudes attained by the holdingcapacitance 7808 are significantly less than the amplitudes of thedown-converted signal illustrated in FIGS. 80D and 80E.

In FIGS. 80E and 80F, the output signal, non-filtered or filtered,cannot provide optimal voltage reproduction, and has relativelynegligible power available at the output (e.g.: V²/R; ˜150 μV and 2KOhms), given the input EM signal 7804 would typically have a drivingimpedance, in an RF environment, of 50 Ohms (e.g.: V²/R; ˜5 mV and 50Ohms).

In summary, under-sampling systems, such as the under-sampling system7802 illustrated in FIG. 78, are well suited for down-converting EMsignals with relatively accurate voltage reproduction. Also, they have anegligible affect on the original input EM signal. As illustrated above,however, the under-sampling systems, such as the under-sampling system7802 illustrated in FIG. 78, are not well suited for transferring energyor for driving lower impedance loads.

-   -   1.2 Introduction to Energy Transfer

In an embodiment, the present invention transfers energy from an EMsignal by utilizing an energy transfer signal instead of anunder-sampling signal. Unlike under-sampling signals that havenegligible aperture pulses, the energy transfer signal includes a trainof pulses having non-negligible apertures that tend away from zero. Thisprovides more time to transfer energy from an EM input signal. Onedirect benefit is that the input impedance of the system is reduced sothat practical impedance matching circuits can be implemented to furtherimprove energy transfer and thus overall efficiency. The non-negligibletransferred energy significantly improves the signal to noise ratio andsensitivity to very small signals, as well as permitting thedown-converted signal to drive lower impedance loads unassisted. Signalsthat especially benefit include low power ones typified by RF signals.One benefit of a non-negligible aperture is that phase noise within theenergy transfer signal does not have as drastic of an effect on thedown-converted output signal as under-sampling signal phase noise orconventional sampling signal phase noise does on their respectiveoutputs.

FIG. 82A illustrates an exemplary energy transfer system 8202 fordown-converting an input EM signal 8204. The energy transfer system 8202includes a switching module 8206 and a storage module illustrated as astorage capacitance 8208. The terms storage module and storagecapacitance, as used herein, are distinguishable from the terms holdingmodule and holding capacitance, respectively. Holding modules andholding capacitances, as used above, identify systems that storenegligible amounts of energy from an under-sampled input EM signal withthe intent of “holding” a voltage value. Storage modules and storagecapacitances, on the other hand, refer to systems that storenon-negligible amounts of energy from an input EM signal.

The energy transfer system 8202 receives an energy transfer signal 8210,which controls the switch module 8206. The energy transfer signal 8210includes a train of energy transfer pulses having non-negligible pulsewidths that tend away from zero time in duration. The non-negligiblepulse widths can be any non-negligible amount. For example, thenon-negligible pulse widths can be ½ of a period of the input EM signal.Alternatively, the non-negligible pulse widths can be any other fractionof a period of the input EM signal, or a multiple of a period plus afraction. In an example embodiment, the input EM signal is approximately900 MHZ and the non-negligible pulse width is approximately 550 picoseconds. Any other suitable non-negligible pulse duration can be used.

In an energy transfer environment, the storage module, illustrated inFIG. 82 as a storage capacitance 8208, preferably has the capacity tohandle the power being transferred, and to allow it to accept anon-negligible amount of power during a non-negligible aperture period.This allows the storage capacitance 8208 to store energy transferredfrom the input EM signal 8204, without substantial concern foraccurately reproducing the original, unaffected voltage level of theinput EM signal 8204. For example, in an embodiment, the storagecapacitance 8208 has a value in the range of 18 pF. Other suitablecapacitance values and storage modules can be used.

One benefit of the energy transfer system 8202 is that, even when theinput EM signal 8204 is a very small signal, the energy transfer system8202 transfers enough energy from the input EM signal 8204 that theinput EM signal can be efficiently down-converted.

The energy transfer system 8202 is coupled to a load 8212. Recall fromthe overview of under-sampling that loads can be classified as highimpedance loads or low impedance loads. A high impedance load is onethat is relatively insignificant to an output drive impedance of thesystem for a given output frequency. A low impedance load is one that isrelatively significant. Another benefit of the energy transfer system8202 is that the non-negligible amounts of transferred energy permit theenergy transfer system 8202 to effectively drive loads that wouldotherwise be classified as low impedance loads in under-sampling systemsand conventional sampling systems. In other words, the non-negligibleamounts of transferred energy ensure that, even for lower impedanceloads, the storage capacitance 8208 accepts and maintains sufficientenergy or charge to drive the load 8202. This is illustrated below inthe timing diagrams of FIGS. 83A–F.

FIGS. 83A–F illustrate example timing diagrams for the energy transfersystem 8202 in FIG. 82. FIG. 83A illustrates an example input EM signal8302.

FIG. 83C illustrates an example energy transfer signal 8304, includingenergy transfer pulses 8306 having non-negligible apertures that tendaway from zero time in duration.

FIG. 83B illustrates the effects to the input EM signal 8302, asmeasured at a terminal 8214 in FIG. 82A, when non-negligible amounts ofenergy are transfered from it. In FIG. 83B, non-negligible distortions8308 correlate with the energy transfer pulses 8306 in FIG. 83C. In thisexample, the non-negligible distortions 8308 occur at differentlocations of subsequent cycles of the input EM signal 8302. Thenon-negligible distortions 8308 represent non-negligible amounts oftransferred energy, in the form of charge that is transferred to thestorage capacitance 8208 in FIG. 82.

FIG. 83D illustrates a down-converted signal 8310 that is formed byenergy transferred from the input EM signal 8302.

FIG. 83E illustrates the down-converted signal 8310 on a compressed timescale. The down-converted signal 8310 can be filtered to produce thedown-converted signal 8312 illustrated in FIG. 83F. The down-convertedsignal 8312 is similar to the down-converted signal illustrated in FIG.79F, except that the down-converted signal 8312 has substantially morepower (e.g.: V²/R; approximately (˜) 2 mV and 2 K Ohms) than thedown-converted signal illustrated in FIG. 79F (e.g.: V²/R; ˜5 mV and 1 MOhms). As a result, the down-converted signals 8310 and 8312 canefficiently drive lower impedance loads, given the input EM signal 8204would typically have a driving impedance, in an RF environment, of 50Ohms (V²/R; ˜5 mV and 50 Ohms).

The energy transfer aspects of the invention are represented generallyby 4506 in FIGS. 45A and 45B.

2. Down-Converting an EM Signal to an IF EM Signal by TransferringEnergy from the EM Signal at an Aliasing Rate

In an embodiment, the invention down-converts an EM signal to an IFsignal by transferring energy from the EM signal at an aliasing rate.This embodiment is illustrated by 4514 in FIG. 45B.

This embodiment can be implemented with any type of EM signal,including, but not limited to, modulated carrier signals and unmodulatedcarrier signals. This embodiment is described herein using the modulatedcarrier signal F_(MC) in FIG. 1 as an example. In the example, themodulated carrier signal F_(MC) is down-converted to an intermediatefrequency (IF) signal F_(IF). The intermediate frequency signal F_(IF)can be demodulated to a baseband signal F_(DMB) using conventionaldemodulation techniques. Upon reading the disclosure and examplestherein, one skilled in the relevant art(s) will understand that theinvention can be implemented to down-convert any EM signal, including,but not limited to, modulated carrier signals and umnodulated carriersignals.

The following sections describe methods for down-converting an EM signalto an IF signal F_(IF) by transferring energy from the EM signal at analiasing rate. Exemplary structural embodiments for implementing themethods are also described. It should be understood that the inventionis not limited to the particular embodiments described below.Equivalents, extensions, variations, deviations, etc., of the followingwill be apparent to persons skilled in the relevant art(s) based on theteachings contained herein. Such equivalents, extensions, variations,deviations, etc., are within the scope and spirit of the presentinvention.

The following sections include a high level discussion, exampleembodiments, and implementation examples.

-   -   2.1 High Level Description

This section (including its subsections) provides a high-leveldescription of down-converting an EM signal to an IF signal F_(IF) bytransferring energy, according to the invention. In particular, anoperational process of down-converting the modulated carrier signalF_(MC) to the IF modulated carrier signal F_(IF), by transferringenergy, is described at a high-level. Also, a structural implementationfor implementing this process is described at a high-level. Thisstructural implementation is described herein for illustrative purposes,and is not limiting. In particular, the process described in thissection can be achieved using any number of structural implementations,one of which is described in this section. The details of suchstructural implementations will be apparent to persons skilled in therelevant art(s) based on the teachings contained herein.

-   -   -   2.1.1 Operational Description

FIG. 46B depicts a flowchart 4607 that illustrates an exemplary methodfor down-converting an EM signal to an intermediate signal F_(IF), bytransferring energy from the EM signal at an aliasing rate. Theexemplary method illustrated in the flowchart 4607 is an embodiment ofthe flowchart 4601 in FIG. 46A.

Any and all combinations of modulation techniques are valid for thisinvention. For ease of discussion, the digital AM carrier signal 616 isused to illustrate a high level operational description of theinvention. Subsequent sections provide detailed flowcharts anddescriptions for AM, FM and PM example embodiments. Upon reading thedisclosure and examples therein, one skilled in the relevant art(s) willunderstand that the invention can be implemented to down-convert anytype of EM signal, including any form of modulated carrier signal andunmodulated carrier signals.

The method illustrated in the flowchart 4607 is now described at a highlevel using the digital AM carrier signal 616 of FIG. 6C. Subsequentsections provide detailed flowcharts and descriptions for AM, FM and PMexample embodiments. Upon reading the disclosure and examples therein,one skilled in the relevant art(s) will understand that the inventioncan be implemented to down-convert any type of EM signal, including anyform of modulated carrier signal and unmodulated carrier signals.

The process begins at step 4608, which includes receiving an EM signal.Step 4608 is illustrated by the digital AM carrier signal 616. Thedigital AM carrier signal 616 of FIG. 6C is re-illustrated in FIG. 47Afor convenience. FIG. 47E illustrates a portion of the digital AMcarrier signal 616 on an expanded time scale.

Step 4610 includes receiving an energy transfer signal having analiasing rate F_(AR). FIG. 47B illustrates an example energy transfersignal 4702. The energy transfer signal 4702 includes a train of energytransfer pulses 4704 having non-negligible apertures 4701 that tend awayfrom zero time duration. Generally, the apertures 4701 can be any timeduration other than the period of the EM signal. For example, theapertures 4701 can be greater or less than a period of the EM signal.Thus, the apertures 4701 can be approximately 1/10, ¼, ½, ¾, etc., orany other fraction of the period of the EM signal. Alternatively, theapertures 4701 can be approximately equal to one or more periods of theEM signal plus 1/10, ¼, ½, ¾, etc., or any other fraction of a period ofthe EM signal. The apertures 4701 can be optimized based on one or moreof a variety of criteria, as described in sections below.

The energy transfer pulses 4704 repeat at the aliasing rate. A suitablealiasing rate can be determined or selected as described below.Generally, when down-converting an EM signal to an intermediate signal,the aliasing rate is substantially equal to a difference frequency,which is described below, or substantially equal to a harmonic or, moretypically, a sub-harmonic of the difference frequency.

Step 4612 includes transferring energy from the EM signal at thealiasing rate to down-convert the EM signal to the intermediate signalF_(IF). FIG. 47C illustrates transferred energy 4706, which istransferred from the EM signal during the energy transfer pulses 4704.Because a harmonic of the aliasing rate occurs at an off-set of thefrequency of the AM signal 616, the pulses 4704 “walk through” the AMsignal 616 at the off-set frequency. By “walking through” the AM signal616, the transferred energy 4706 forms an AM intermediate signal 4706that is similar to the AM carrier signal 616, except that the AMintermediate signal has a lower frequency than the AM carrier signal616. The AM carrier signal 616 can be down-converted to any frequencybelow the AM carrier signal 616 by adjusting the aliasing rate F_(AR),as described below.

FIG. 47D depicts the AM intermediate signal 4706 as a filtered outputsignal 4708. In an alternative embodiment, the invention outputs a stairstep, or non-filtered output signal. The choice between filtered,partially filtered and non-filtered output signals is generally a designchoice that depends upon the application of the invention.

The intermediate frequency of the down-converted signal F_(IF), which,in this example, is the intermediate signal 4706 and 4708, can bedetermined from EQ. (2), which is reproduced below for convenience.F _(C) =n·F _(AR) ±F _(IF)  EQ. (2)

A suitable aliasing rate F_(AR) can be determined in a variety of ways.An example method for determining the aliasing rate F_(AR), is providedbelow. After reading the description herein, one skilled in the relevantart(s) will understand how to determine appropriate aliasing rates forEM signals, including ones in addition to the modulated carrier signalsspecifically illustrated herein.

In FIG. 48, a flowchart 4801 illustrates an example process fordetermining an aliasing rate F_(AR). But a designer may choose, or anapplication may dictate, that the values be determined in an order thatis different than the illustrated order. The process begins at step4802, which includes determining, or selecting, the frequency of the EMsignal. The frequency of the AM carrier signal 616 can be, for example,901 MHZ.

Step 4804 includes determining, or selecting, the intermediatefrequency. This is the frequency to which the EM signal will bedown-converted The intermediate frequency can be determined, orselected, to match a frequency requirement of a down-stream demodulator.The intermediate frequency can be, for example, 1 MHZ.

Step 4806 includes determining the aliasing rate or rates that willdown-convert the EM signal to the IF specified in step 4804.

EQ. (2) can be rewritten as EQ. (3):n·F _(AR) =F _(C) ±F _(IF)  EQ. (3)

Which can be rewritten as EQ. (4):

$\begin{matrix}{n = \frac{F_{C} \pm F_{IF}}{F_{AR}}} & {{EQ}.\mspace{20mu}(4)}\end{matrix}$

or as EQ. (5):

$\begin{matrix}{F_{AR} = \frac{F_{C} \pm F_{IF}}{n}} & {{EQ}.\mspace{20mu}(5)}\end{matrix}$

(F_(C)±F_(IF)) can be defined as a difference value F_(DIFF), asillustrated in EQ. (6):(F _(C) ±F _(IF))=F _(DIFF)  EQ. (6)

EQ. (4) can be rewritten as EQ. (7):

$\begin{matrix}{n = \frac{F_{DIFF}}{F_{AR}}} & {{EQ}.\mspace{20mu}(7)}\end{matrix}$

From EQ. (7), it can be seen that, for a given n and a constant F_(AR),F_(DIFF) is constant. For the case of F_(DIFF)=F_(C)−F_(IF), and for aconstant F_(DIFF), as F_(C) increases, F_(IF) necessarily increases. Forthe case of F_(DIFF)=F_(C)+F_(IF), and for a constant F_(DIFF), as F_(C)increases, F_(IF) necessarily decreases. In the latter case ofF_(DIFF)=F_(C)+F_(IF), any phase or frequency changes on F_(C)correspond to reversed or inverted phase or frequency changes on F_(IF).This is mentioned to teach the reader that if F_(DIFF)=F_(C)+F_(IF) isused, the above effect will occur to the phase and frequency response ofthe modulated intermediate signal F_(IF).

EQs. (2) through (7) can be solved for any valid n. A suitable n can bedetermined for any given difference frequency F_(DIFF) and for anydesired aliasing rate F_(AR(Desired)). EQs. (2) through (7) can beutilized to identify a specific harmonic closest to a desired aliasingrate F_(AR(Desired)) that will generate the desired intermediate signalF_(IF).

An example is now provided for determining a suitable n for a givendifference frequency F_(DIFF) and for a desired aliasing rateF_(AR(Desired)). For ease of illustration, only the case of(F_(C)−F_(IF)) is illustrated in the example below.

$n = {\frac{F_{C} - F_{IF}}{F_{{AR}_{({Desired})}}} = \frac{F_{DIFF}}{F_{{AR}_{({Desired})}}}}$

The desired aliasing rate F_(AR(Desired)) can be, for example, 140 MHZ.Using the previous examples, where the carrier frequency is 901 MHZ andthe IF is 1 MHZ, an initial value of n is determined as:n=901 MHZ−1 MHZ/140 MHZ=900/140=6.4

The initial value 6.4 can be rounded up or down to the valid nearest n,which was defined above as including (0.5, 1, 2, 3, . . . ). In thisexample, 6.4 is rounded down to 6.0, which is inserted into EQ. (5) forthe case of (F_(C)−F_(IF))=F_(DIFF).:

$F_{AR} = \frac{F_{c} - F_{IF}}{n}$$F_{AR} = {\frac{{901\mspace{14mu}{MHZ}} - {1\mspace{14mu}{MHZ}}}{6} = {\frac{900\mspace{14mu}{MHZ}}{6} = {150\mspace{14mu}{MHZ}}}}$

In other words, transferring energy from a 901 MHZ EM carrier signal at150 MHZ generates an intermediate signal at 1 MHZ. When the EM carriersignal is a modulated carrier signal, the intermediate signal will alsosubstantially include the modulation. The modulated intermediate signalcan be demodulated through any conventional demodulation technique.

Alternatively, instead of starting from a desired aliasing rate, a listof suitable aliasing rates can be determined from the modified form ofEQ. (5), by solving for various values of n. Example solutions arelisted below.

$F_{AR} = {\frac{\left( {F_{C} - F_{IF}} \right)}{n} = {\frac{F_{DIFF}}{n} = {\frac{{901\mspace{14mu}{MHZ}} - {1\mspace{14mu}{MHZ}}}{n} = \frac{900\mspace{14mu}{MHZ}}{n}}}}$

Solving for n=0.5, 1, 2, 3, 4, 5 and 6:

900 MHZ/0.5=1.8 GHZ (i.e., second harmonic);

900 MHZ/1=900 MHZ (i.e., fundamental frequency);

900 MHZ/2=450 MHZ (i.e., second sub-harmonic);

900 MHZ/3=300 MHZ (i.e., third sub-harmonic);

900 MHZ/4=225 MHZ (i.e., fourth sub-harmonic);

900 MHZ/5=180 MHZ(i.e., fifth sub-harmonic); and

900 MHZ/6=150 MHZ(i.e., sixth sub-harmonic).

The steps described above can be performed for the case of(F_(C)+F_(IF)) in a similar fashion. The results can be compared to theresults obtained from the case of (F_(C)−F_(IF)) to determine whichprovides better result for an application.

In an embodiment, the invention down-converts an EM signal to arelatively standard IF in the range of, for example, 100 KHZ to 200 MHZ.In another embodiment, referred to herein as a small off-setimplementation, the invention down-converts an EM signal to a relativelylow frequency of, for example, less than 100 KHZ. In another embodiment,referred to herein as a large off-set implementation, the inventiondown-converts an EM signal to a relatively higher IF signal, such as,for example, above 200 MHZ.

The various off-set implementations provide selectivity for differentapplications. Generally, lower data rate applications can operate atlower intermediate frequencies. But higher intermediate frequencies canallow more information to be supported for a given modulation technique.

In accordance with the invention, a designer picks an optimuminformation bandwidth for an application and an optimum intermediatefrequency to support the baseband signal. The intermediate frequencyshould be high enough to support the bandwidth of the modulatingbaseband signal F_(MB).

Generally, as the aliasing rate approaches a harmonic or sub-harmonicfrequency of the EM signal, the frequency of the down-converted IFsignal decreases. Similarly, as the aliasing rate moves away from aharmonic or sub-harmonic frequency of the EM signal, the IF increases.

Aliased frequencies occur above and below every harmonic of the aliasingfrequency. In order to avoid mapping other aliasing frequencies in theband of the aliasing frequency (IF) of interest, the IF of interestshould not be near one half the aliasing rate.

As described in example implementations below, an aliasing module,including a universal frequency translator (UFT) module built inaccordance with the invention provides a wide range of flexibility infrequency selection and can thus be implemented in a wide range ofapplications. Conventional systems cannot easily offer, or do not allow,this level of flexibility in frequency selection.

-   -   -   2.1.2 Structural Description

FIG. 63 illustrates a block diagram of an energy transfer system 6302according to an embodiment of the invention. The energy transfer system6302 is an example embodiment of the generic aliasing system 1302 inFIG. 13. The energy transfer system 6302 includes an energy transfermodule 6304. The energy transfer module 6304 receives the EM signal 1304and an energy transfer signal 6306, which includes a train of energytransfer pulses having non-negligible apertures that tend away from zerotime in duration, occurring at a frequency equal to the aliasing rateF_(AR). The energy transfer signal 6306 is an example embodiment of thealiasing signal 1310 in FIG. 13. The energy transfer module 6304transfers energy from the EM signal 1304 at the aliasing rate F_(AR) ofthe energy transfer signal 6306.

Preferably, the energy transfer module 6304 transfers energy from the EMsignal 1304 to down-convert it to the intermediate signal F_(IF) in themanner shown in the operational flowchart 4607 of FIG. 46B. But itshould be understood that the scope and spirit of the invention includesother structural embodiments for performing the steps of the flowchart4607. The specifics of the other structural embodiments will be apparentto persons skilled in the relevant art(s) based on the discussioncontained herein.

The operation of the energy transfer system 6302 is now described indetail with reference to the flowchart 4607 and to the timing diagramsillustrated in FIGS. 47A–E. In step 4608, the energy transfer module6304 receives the AM carrier signal 616. In step 4610, the energytransfer module 6304 receives the energy transfer signal 4702. In step4612, the energy transfer module 6304 transfers energy from the AMcarrier signal 616 at the aliasing rate to down-convert the AM carriersignal 616 to the intermediate signal 4706 or 4708.

Example implementations of the energy transfer system 6302 are providedin Sections 4 and 5 below.

-   -   2.2 Example Embodiments

Various embodiments related to the method(s) and structure(s) describedabove are presented in this section (and its subsections). Theseembodiments are described herein for purposes of illustration, and notlimitation. The invention is not limited to these embodiments. Alternateembodiments (including equivalents, extensions, variations, deviations,etc., of the embodiments described herein) will be apparent to personsskilled in the relevant art(s) based on the teachings contained herein.The invention is intended and adapted to include such alternateembodiments.

The method for down-converting the EM signal 1304 by transferring energycan be implemented with any type of EM signal, including modulatedcarrier signals and unmodulated carrier signals. For example, the methodof the flowchart 4601 can be implemented to down-convert AM signals, FMsignals, PM signals, etc., or any combination thereof. Operation of theflowchart 4601 of FIG. 46A is described below for down-converting AM, FMand PM. The down-conversion descriptions include down-converting tointermediate signals, directly down-converting to demodulated basebandsignals, and down-converting FM signals to non-FM signals. The exemplarydescriptions below are intended to facilitate an understanding of thepresent invention. The present invention is not limited to or by theexemplary embodiments below.

-   -   -   2.2.1 First Example Embodiment: Amplitude Modulation            -   2.2.1.1 Operational Description

Operation of the exemplary process of the flowchart 4607 in FIG. 46B isdescribed below for the analog AM carrier signal 516, illustrated inFIG. 5C, and for the digital AM carrier signal 616, illustrated in FIG.6C.

-   -   -   -   -   2.2.1.1.1 Analog AM Carrier Signal

A process for down-converting the analog AM carrier signal 516 in FIG.5C to an analog AM intermediate signal is now described for theflowchart 4607 in FIG. 46B. The analog AM carrier signal 516 isre-illustrated in FIG. 50A for convenience. For this example, the analogAM carrier signal 516 oscillates at approximately 901 MHZ. In FIG. 50B,an analog AM carrier signal 5004 illustrates a portion of the analog AMcarrier signal 516 on an expanded time scale.

The process begins at step 4608, which includes receiving the EM signal.This is represented by the analog AM carrier signal 516.

Step 4610 includes receiving an energy transfer signal having analiasing rate F_(AR). FIG. 50C illustrates an example energy transfersignal 5006 on approximately the same time scale as FIG. 50B. The energytransfer signal 5006 includes a train of energy transfer pulses 5007having non-negligible apertures 5009 that tend away from zero time induration. The energy transfer pulses 5007 repeat at the aliasing rateF_(AR), which is determined or selected as previously described.Generally, when down-converting to an intermediate signal, the aliasingrate F_(AR) is substantially equal to a harmonic or, more typically, asub-harmonic of the difference frequency F_(DIFF).

Step 4612 includes transferring energy from the EM signal at thealiasing rate to down-convert the EM signal to an intermediate signalF_(IF). In FIG. 50D, an affected analog AM carrier signal 5008illustrates effects of transferring energy from the analog AM carriersignal 516 at the aliasing rate F_(AR). The affected analog AM carriersignal 5008 is illustrated on substantially the same time scale as FIGS.50B and 50C.

FIG. 50E illustrates a down-converted AM intermediate signal 5012, whichis generated by the down-conversion process. The AM intermediate signal5012 is illustrated with an arbitrary load impedance. Load impedanceoptimizations are discussed in Section 5 below.

The down-converted signal 5012 includes portions 5010A, which correlatewith the energy transfer pulses 5007 in FIG. 50C, and portions 5010B,which are between the energy transfer pulses 5007. Portions 5010Arepresent energy transferred from the AM analog signal 516 to a storagedevice, while simultaneously driving an output load. The portions 5010Aoccur when a switching module is closed by the energy transfer pulses5007. Portions 5010B represent energy stored in a storage devicecontinuing to drive the load. Portions 5010B occur when the switchingmodule is opened after energy transfer pulses 5007.

Because a harmonic of the aliasing rate is off-set from the analog AMcarrier signal 516, the energy transfer pulses 5007 “walk through” theanalog AM carrier signal 516 at the difference frequency F_(DIFF). Inother words, the energy transfer pulses 5007 occur at differentlocations of subsequent cycles of the AM carrier signal 516. As aresult, the energy transfer pulses 5007 capture varying amounts ofenergy from the analog AM carrier signal 516, as illustrated by portions5010A, which provides the AM intermediate signal 5012 with anoscillating frequency F_(IF).

In FIG. 50F, an AM intermediate signal 5014 illustrates the AMintermediate signal 5012 on a compressed time scale. In FIG. 50G, an AMintermediate signal 5016 represents a filtered version of the AMintermediate signal 5014. The AM intermediate signal 5016 issubstantially similar to the AM carrier signal 516, except that the AMintermediate signal 5016 is at the intermediate frequency. The AMintermediate signal 5016 can be demodulated through any conventionaldemodulation technique.

The present invention can output the unfiltered AM intermediate signal5014, the filtered AM intermediate signal 5016, a partially filtered AMintermediate signal, a stair step output signal, etc. The choice betweenthese embodiments is generally a design choice that depends upon theapplication of the invention.

The signals referred to herein illustrate frequency down-conversion inaccordance with the invention. For example, the AM intermediate signals5014 in FIG. 50F and 5016 in FIG. 50G illustrate that the AM carriersignal 516 was successfully down-converted to an intermediate signal byretaining enough baseband information for sufficient reconstruction.

-   -   -   -   -   2.2.1.2.2 Digital AM Carrier Signal

A process for down-converting the digital AM carrier signal 616 to adigital AM intermediate signal is now described for the flowchart 4607in FIG. 46B. The digital AM carrier signal 616 is re-illustrated in FIG.51A for convenience. For this example, the digital AM carrier signal 616oscillates at approximately 901 MHZ. In FIG. 51B, a digital AM carriersignal 5104 illustrates a portion of the digital AM carrier signal 616on an expanded time scale.

The process begins at step 4608, which includes receiving an EM signal.This is represented by the digital AM carrier signal 616.

Step 4610 includes receiving an energy transfer signal having analiasing rate F_(AR). FIG. 51C illustrates an example energy transfersignal 5106 on substantially the same time scale as FIG. 51B. The energytransfer signal 5106 includes a train of energy transfer pulses 5107having non-negligible apertures 5109 that tend away from zero time induration. The energy transfer pulses 5107 repeat at the aliasing rate,which is determined or selected as previously described. Generally, whendown-converting to an intermediate signal, the aliasing rate issubstantially equal to a harmonic or, more typically, a sub-harmonic ofthe difference frequency F_(DIFF).

Step 4612 includes transferring energy from the EM signal at thealiasing rate to down-convert the EM signal to the intermediate signalF_(IF). In FIG. 51D, an affected digital AM carrier signal 5108illustrates effects of transferring energy from the digital AM carriersignal 616 at the aliasing rate F_(AR). The affected digital AM carriersignal 5108 is illustrated on substantially the same time scale as FIGS.51B and 51C.

FIG. 51E illustrates a down-converted AM intermediate signal 5112, whichis generated by the down-conversion process. The AM intermediate signal5112 is illustrated with an arbitrary load impedance. Load impedanceoptimizations are discussed in Section 5 below.

The down-converted signal 5112 includes portions 5110A, which correlatewith the energy transfer pulses 5107 in FIG. 51C, and portions 5110B,which are between the energy transfer pulses 5107. Portions 5110Arepresent energy transferred from the digital AM carrier signal 616 to astorage device, while simultaneously driving an output load. Theportions 5110A occur when a switching module is closed by the energytransfer pulses 5107. Portions 5110B represent energy stored in astorage device continuing to drive the load. Portions 5110B occur whenthe switching module is opened after energy transfer pulses 5107.

Because a harmonic of the aliasing rate is off-set from the frequency ofthe digital AM carrier signal 616, the energy transfer pulses 5107 “walkthrough” the digital AM signal 616 at the difference frequency F_(DIFF).In other words, the energy transfer pulse 5107 occur at differentlocations of subsequent cycles of the digital AM carrier signal 616. Asa result, the energy transfer pulses 5107 capture varying amounts ofenergy from the digital AM carrier signal 616, as illustrated byportions 5110, which provides the AM intermediate signal 5112 with anoscillating frequency F_(IF).

In FIG. 51F, a digital AM intermediate signal 5114 illustrates the AMintermediate signal 5112 on a compressed time scale. In FIG. 51G, an AMintermediate signal 5116 represents a filtered version of the AMintermediate signal 5114. The AM intermediate signal 5116 issubstantially similar to the AM carrier signal 616, except that the AMintermediate signal 5116 is at the intermediate frequency. The AMintermediate signal 5116 can be demodulated through any conventionaldemodulation technique.

The present invention can output the unfiltered AM intermediate signal5114, the filtered AM intermediate signal 5116, a partially filtered AMintermediate signal, a stair step output signal, etc. The choice betweenthese embodiments is generally a design choice that depends upon theapplication of the invention.

The signals referred to herein illustrate frequency down-conversion inaccordance with the invention. For example, the AM intermediate signals5114 in FIGS. 51F and 5116 in FIG. 51G illustrate that the AM carriersignal 616 was successfully down-converted to an intermediate signal byretaining enough baseband information for sufficient reconstruction.

-   -   -   -   2.2.1.2 Structural Description

The operation of the energy transfer system 6302 is now described forthe analog AM carrier signal 516, with reference to the flowchart 4607and to the timing diagrams in FIGS. 50A–G. In step 4608, the energytransfer module 6304 receives the analog AM carrier signal 516. In step4610, the energy transfer module 6304 receives the energy transfersignal 5006. In step 4612, the energy transfer module 6304 transfersenergy from the analog AM carrier signal 516 at the aliasing rate of theenergy transfer signal 5006, to down-convert the analog AM carriersignal 516 to the AM intermediate signal 5012.

The operation of the energy transfer system 6302 is now described forthe digital AM carrier signal 616, with reference to the flowchart 1401and the timing diagrams in FIGS. 51A–G. In step 4608, the energytransfer module 6304 receives the digital AM carrier signal 616. In step4610, the energy transfer module 6304 receives the energy transfersignal 5106. In step 4612, the energy transfer module 6304 transfersenergy from the digital AM carrier signal 616 at the aliasing rate ofthe energy transfer signal 5106, to down-convert the digital AM carriersignal 616 to the AM intermediate signal 5112.

Example embodiments of the energy transfer module 6304 are disclosed inSections 4 and 5 below.

-   -   -   2.2.2 Second Example Embodiment: Frequency Modulation            -   2.2.2.1 Operational Description

Operation of the exemplary process of the flowchart 4607 in FIG. 46B isdescribed below for the analog FM carrier signal 716, illustrated inFIG. 7C, and for the digital FM carrier signal 816, illustrated in FIG.8C.

-   -   -   -   -   2.2.2.1.1 Analog FM Carrier Signal

A process for down-converting the analog FM carrier signal 716 in FIG.7C to an FM intermediate signal is now described for the flowchart 4607in FIG. 46B. The analog FM carrier signal 716 is re-illustrated in FIG.52A for convenience. For this example, the analog FM carrier signal 716oscillates around approximately 901 MHZ. In FIG. 52B, an analog FMcarrier signal 5204 illustrates a portion of the analog FM carriersignal 716 on an expanded time scale.

The process begins at step 4608, which includes receiving an EM signal.This is represented by the analog FM carrier signal 716.

Step 4610 includes receiving an energy transfer signal having analiasing rate F_(AR). FIG. 52C illustrates an example energy transfersignal 5206 on approximately the same time scale as FIG. 52B. The energytransfer signal 5206 includes a train of energy transfer pulses 5207having non-negligible apertures that tend away from zero time induration. The energy transfer pulses 5207 repeat at the aliasing rateF_(AR), which is determined or selected as previously described.Generally, when down-converting to an intermediate signal, the aliasingrate F_(AR) is substantially equal to a harmonic or, more typically, asub-harmonic of the difference frequency F_(DIFF).

Step 4612 includes transferring energy from the EM signal at thealiasing rate to down-convert the EM signal to an intermediate signalF_(IF). In FIG. 52D, an affected analog FM carrier signal 5208illustrates effects of transferring energy from the analog FM carriersignal 716 at the aliasing rate F_(AR). The affected analog FM carriersignal 5208 is illustrated on substantially the same time scale as FIGS.52B and 52C.

FIG. 52E illustrates a down-converted FM intermediate signal 5212, whichis generated by the down-conversion process. The FM intermediate signal5212 is illustrated with an arbitrary load impedance. Load impedanceoptimizations are discussed in Section 5 below.

The down-converted signal 5212 includes portions 5210A, which correlatewith the energy transfer pulses 5207 in FIG. 52C, and portions 5210B,which are between the energy transfer pulses 5207. Portions 5210Arepresent energy transferred from the analog FM carrier signal 716 to astorage device, while simultaneously driving an output load. Theportions 5210A occur when a switching module is closed by the energytransfer pulses 5207. Portions 5210B represent energy stored in astorage device continuing to drive the load. Portions 5210B occur whenthe switching module is opened after energy transfer pulses 5207.

Because a harmonic of the aliasing rate is off-set from the frequency ofthe analog FM carrier signal 716, the energy transfer pulses 5207 “walkthrough” the analog FM carrier signal 716 at the difference frequencyF_(DIFF). In other words, the energy transfer pulse 5207 occur atdifferent locations of subsequent cycles of the analog FM carrier signal716. As a result, the energy transfer pulses 5207 capture varyingamounts of energy from the analog FM carrier signal 716, as illustratedby portions 5210, which provides the FM intermediate signal 5212 with anoscillating frequency F_(IF).

In FIG. 52F, an analog FM intermediate signal 5214 illustrates the FMintermediate signal 5212 on a compressed time scale. In FIG. 52G, an FMintermediate signal 5216 represents a filtered version of the FMintermediate signal 5214. The FM intermediate signal 5216 issubstantially similar to the analog FM carrier signal 716, except thatthe FM intermediate signal 5216 is at the intermediate frequency. The FMintermediate signal 5216 can be demodulated through any conventionaldemodulation technique.

The present invention can output the unfiltered FM intermediate signal5214, the filtered FM intermediate signal 5216, a partially filtered FMintermediate signal, a stair step output signal, etc. The choice betweenthese embodiments is generally a design choice that depends upon theapplication of the invention.

The signals referred to herein illustrate frequency down-conversion inaccordance with the invention. For example, the FM intermediate signals5214 in FIGS. 52F and 5216 in FIG. 52G illustrate that the FM carriersignal 716 was successfully down-converted to an intermediate signal byretaining enough baseband information for sufficient reconstruction.

-   -   -   -   -   2.2.2.1.2 Digital FM Carrier Signal

A process for down-converting the digital FM carrier signal 816 in FIG.8C is now described for the flowchart 4607 in FIG. 46B. The digital FMcarrier signal 816 is re-illustrated in FIG. 53A for convenience. Forthis example, the digital FM carrier signal 816 oscillates atapproximately 901 MHZ. In FIG. 53B, a digital FM carrier signal 5304illustrates a portion of the digital FM carrier signal 816 on anexpanded time scale.

The process begins at step 4608, which includes receiving an EM signal.This is represented by the digital FM carrier signal 816.

Step 4610 includes receiving an energy transfer signal having analiasing rate F_(AR). FIG. 53C illustrates an example energy transfersignal 5306 on substantially the same time scale as FIG. 53B. The energytransfer signal 5306 includes a train of energy transfer pulses 5307having non-negligible apertures 5309 that tend away from zero time induration. The energy transfer pulses 5307 repeat at the aliasing rate,which is determined or selected as previously described. Generally, whendown-converting to an intermediate signal, the aliasing rate F_(AR) issubstantially equal to a harmonic or, more typically, a sub-harmonic ofthe difference frequency F_(DIFF).

Step 4612 includes transferring energy from the EM signal at thealiasing rate to down-convert the EM signal to the an intermediatesignal F_(IF). In FIG. 53D, an affected digital FM carrier signal 5308illustrates effects of transferring energy from the digital FM carriersignal 816 at the aliasing rate F_(AR). The affected digital FM carriersignal 5308 is illustrated on substantially the same time scale as FIGS.53B and 53C.

FIG. 53E illustrates a down-converted FM intermediate signal 5312, whichis generated by the down-conversion process. The down-converted signal5312 includes portions 5310A, which correlate with the energy transferpulses 5307 in FIG. 53C, and portions 5310B, which are between theenergy transfer pulses 5307. Down-converted signal 5312 is illustratedwith an arbitrary load impedance. Load impedance optimizations arediscussed in Section 5 below.

Portions 5310A represent energy transferred from the digital FM carriersignal 816 to a storage device, while simultaneously driving an outputload. The portions 5310A occur when a switching module is closed by theenergy transfer pulses 5307.

Portions 5310B represent energy stored in a storage device continuing todrive the load. Portions 5310B occur when the switching module is openedafter energy transfer pulses 5307.

Because a harmonic of the aliasing rate is off-set from the frequency ofthe digital FM carrier signal 816, the energy transfer pulses 5307 “walkthrough” the digital FM carrier signal 816 at the difference frequencyF_(DIFF). In other words, the energy transfer pulse 5307 occur atdifferent locations of subsequent cycles of the digital FM carriersignal 816. As a result, the energy transfer pulses 5307 capture varyingamounts of energy from the digital FM carrier signal 816, as illustratedby portions 5310, which provides the FM intermediate signal 5312 with anoscillating frequency F_(IF).

In FIG. 53F, a digital FM intermediate signal 5314 illustrates the FMintermediate signal 5312 on a compressed time scale. In FIG. 53G, an FMintermediate signal 5316 represents a filtered version of the FMintermediate signal 5314. The FM intermediate signal 5316 issubstantially similar to the digital FM carrier signal 816, except thatthe FM intermediate signal 5316 is at the intermediate frequency. The FMintermediate signal 5316 can be demodulated through any conventionaldemodulation technique.

The present invention can output the unfiltered FM intermediate signal5314, the filtered FM intermediate signal 5316, a partially filtered FMintermediate signal, a stair step output signal, etc. The choice betweenthese embodiments is generally a design choice that depends upon theapplication of the invention.

The signals referred to herein illustrate frequency down-conversion inaccordance with the invention. For example, the FM intermediate signals5314 in FIGS. 53F and 5316 in FIG. 53G illustrate that the FM carriersignal 816 was successfully down-converted to an intermediate signal byretaining enough baseband information for sufficient reconstruction.

-   -   -   -   2.2.2.2 Structural Description

The operation of the energy transfer system 6302 is now described forthe analog FM carrier signal 716, with reference to the flowchart 4607and the timing diagrams in FIGS. 52A–G. In step 4608, the energytransfer module 6304 receives the analog FM carrier signal 716. In step4610, the energy transfer module 6304 receives the energy transfersignal 5206. In step 4612, the energy transfer module 6304 transfersenergy from the analog FM carrier signal 716 at the aliasing rate of theenergy transfer signal 5206, to down-convert the analog FM carriersignal 716 to the FM intermediate signal 5212.

The operation of the energy transfer system 6302 is now described forthe digital FM carrier signal 816, with reference to the flowchart 4607and the timing diagrams in FIGS. 53A–G. In step 4608, the energytransfer module 6304 receives the digital FM carrier signal 816. In step4610, the energy transfer module 6304 receives the energy transfersignal 5306. In step 4612, the energy transfer module 6304 transfersenergy from the digital FM carrier signal 816 at the aliasing rate ofthe energy transfer signal 5306, to down-convert the digital FM carriersignal 816 to the FM intermediate signal 5212.

Example embodiments of the energy transfer module 6304 are disclosed inSections 4 and 5 below.

-   -   -   2.2.3 Third Example Embodiment: Phase Modulation            -   2.2.3.1 Operational Description

Operation of the exemplary process of the flowchart 4607 in FIG. 46B isdescribed below for the analog PM carrier signal 916, illustrated inFIG. 9C, and for the digital PM carrier signal 1016, illustrated in FIG.10C.

-   -   -   -   -   2.2.3.1.1 Analog PM Carrier Signal

A process for down-converting the analog PM carrier signal 916 in FIG.9C to an analog PM intermediate signal is now described for theflowchart 4607 in FIG. 46B. The analog PM carrier signal 916 isre-illustrated in FIG. 54A for convenience. For this example, the analogPM carrier signal 916 oscillates at approximately 901 MHZ. In FIG. 54B,an analog PM carrier signal 5404 illustrates a portion of the analog PMcarrier signal 916 on an expanded time scale.

The process begins at step 4608, which includes receiving an EM signal.This is represented by the analog PM carrier signal 916.

Step 4610 includes receiving an energy transfer signal having analiasing rate F_(AR). FIG. 54C illustrates an example energy transfersignal 5406 on approximately the same time scale as FIG. 54B. The energytransfer signal 5406 includes a train of energy transfer pulses 5407having non-negligible apertures that tend away from zero time induration. The energy transfer pulses 5407 repeat at the aliasing rate,which is determined or selected as previously described. Generally, whendown-converting to an intermediate signal, the aliasing rate F_(AR) issubstantially equal to a harmonic or, more typically, a sub-harmonic ofthe difference frequency F_(DIFF).

Step 4612 includes transferring energy from the EM signal at thealiasing rate to down-convert the EM signal to the IF signal F_(IF). InFIG. 54D, an affected analog PM carrier signal 5408 illustrates effectsof transferring energy from the analog PM carrier signal 916 at thealiasing rate F_(AR). The affected analog PM carrier signal 5408 isillustrated on substantially the same time scale as FIGS. 54B and 54C.

FIG. 54E illustrates a down-converted PM intermediate signal 5412, whichis generated by the down-conversion process. The down-converted PMintermediate signal 5412 includes portions 5410A, which correlate withthe energy transfer pulses 5407 in FIG. 54C, and portions 5410B, whichare between the energy transfer pulses 5407. Down-converted signal 5412is illustrated with an arbitrary load impedance. Load impedanceoptimizations are discussed in Section 5 below.

Portions 5410A represent energy transferred from the analog PM carriersignal 916 to a storage device, while simultaneously driving an outputload. The portions 5410A occur when a switching module is closed by theenergy transfer pulses 5407.

Portions 5410B represent energy stored in a storage device continuing todrive the load. Portions 5410B occur when the switching module is openedafter energy transfer pulses 5407.

Because a harmonic of the aliasing rate is off-set from the frequency ofthe analog PM carrier signal 716, the energy transfer pulses 5407 “walkthrough” the analog PM carrier signal 916 at the difference frequencyF_(DIFF). In other words, the energy transfer pulse 5407 occur atdifferent locations of subsequent cycles of the analog PM carrier signal916. As a result, the energy transfer pulses 5407 capture varyingamounts of energy from the analog PM carrier signal 916, as illustratedby portions 5410, which provides the PM intermediate signal 5412 with anoscillating frequency F_(IF).

In FIG. 54F, an analog PM intermediate signal 5414 illustrates the PMintermediate signal 5412 on a compressed time scale. In FIG. 54G, an PMintermediate signal 5416 represents a filtered version of the PMintermediate signal 5414. The PM intermediate signal 5416 issubstantially similar to the analog PM carrier signal 916, except thatthe PM intermediate signal 5416 is at the intermediate frequency. The PMintermediate signal 5416 can be demodulated through any conventionaldemodulation technique.

The present invention can output the unfiltered PM intermediate signal5414, the filtered PM intermediate signal 5416, a partially filtered PMintermediate signal, a stair step output signal, etc. The choice betweenthese embodiments is generally a design choice that depends upon theapplication of the invention.

The signals referred to herein illustrate frequency down-conversion inaccordance with the invention. For example, the PM intermediate signals5414 in FIGS. 54F and 5416 in FIG. 54G illustrate that the PM carriersignal 916 was successfully down-converted to an intermediate signal byretaining enough baseband information for sufficient reconstruction.

-   -   -   -   -   2.2.3.1.2 Digital PM Carrier Signal

A process for down-converting the digital PM carrier signal 1016 in FIG.10C to a digital PM signal is now described for the flowchart 3607 inFIG. 46B. The digital PM carrier signal 1016 is re-illustrated in FIG.55A for convenience. For this example, the digital PM carrier signal1016 oscillates at approximately 901 MHZ. In FIG. 55B, a digital PMcarrier signal 5504 illustrates a portion of the digital PM carriersignal 1016 on an expanded time scale.

The process begins at step 4608, which includes receiving an EM signal.This is represented by the digital PM carrier signal 1016.

Step 4610 includes receiving an energy transfer signal having analiasing rate F_(AR). FIG. 55C illustrates an example energy transfersignal 5506 on substantially the same time scale as FIG. 55B. The energytransfer signal 5506 includes a train of energy transfer pulses 5507having non-negligible apertures 5509 that tend away from zero time induration. The energy transfer pulses 5507 repeat at an aliasing rate,which is determined or selected as previously described. Generally, whendown-converting to an intermediate signal, the aliasing rate F_(AR) issubstantially equal to a harmonic or, more typically, a sub-harmonic ofthe difference frequency F_(DIFF).

Step 4612 includes transferring energy from the EM signal at thealiasing rate to down-convert the EM signal to an intermediate signalF_(IF). In FIG. 55D, an affected digital PM carrier signal 5508illustrates effects of transferring energy from the digital PM carriersignal 1016 at the aliasing rate F_(AR). The affected digital PM carriersignal 5508 is illustrated on substantially the same time scale as FIGS.55B and 55C.

FIG. 55E illustrates a down-converted PM intermediate signal 5512, whichis generated by the down-conversion process. The down-converted PMintermediate signal 5512 includes portions 5510A, which correlate withthe energy transfer pulses 5507 in FIG. 55C, and portions 5510B, whichare between the energy transfer pulses 5507. Down-converted signal 5512is illustrated with an arbitrary load impedance. Load impedanceoptimizations are discussed in Section 5 below.

Portions 5510A represent energy transferred from the digital PM carriersignal 1016 to a storage device, while simultaneously driving an outputload. The portions 5510A occur when a switching module is closed by theenergy transfer pulses 5507.

Portions 5510B represent energy stored in a storage device continuing todrive the load. Portions 5510B occur when the switching module is openedafter energy transfer pulses 5507.

Because a harmonic of the aliasing rate is off-set from the frequency ofthe digital PM carrier signal 716, the energy transfer pulses 5507 “walkthrough” the digital PM carrier signal 1016 at the difference frequencyF_(DIFF). In other words, the energy transfer pulse 5507 occur atdifferent locations of subsequent cycles of the digital PM carriersignal 1016. As a result, the energy transfer pulses 5507 capturevarying amounts of energy from the digital PM carrier signal 1016, asillustrated by portions 5510, which provides the PM intermediate signal5512 with an oscillating frequency F_(IF).

In FIG. 55F, a digital PM intermediate signal 5514 illustrates the PMintermediate signal 5512 on a compressed time scale. In FIG. 55G, an PMintermediate signal 5516 represents a filtered version of the PMintermediate signal 5514. The PM intermediate signal 5516 issubstantially similar to the digital PM carrier signal 1016, except thatthe PM intermediate signal 5516 is at the intermediate frequency. The PMintermediate signal 5516 can be demodulated through any conventionaldemodulation technique.

The present invention can output the unfiltered PM intermediate signal5514, the filtered PM intermediate signal 5516, a partially filtered PMintermediate signal, a stair step output signal, etc. The choice betweenthese embodiments is generally a design choice that depends upon theapplication of the invention.

The signals referred to herein illustrate frequency down-conversion inaccordance with the invention. For example, the PM intermediate signals5514 in FIGS. 55F and 5516 in FIG. 55G illustrate that the PM carriersignal 1016 was successfully down-converted to an intermediate signal byretaining enough baseband information for sufficient reconstruction.

-   -   -   -   2.2.3.2 Structural Description

Operation of the energy transfer system 6302 is now described for theanalog PM carrier signal 916, with reference to the flowchart 4607 andthe timing diagrams in FIGS. 54A–G. In step 4608, the energy transfermodule 6304 receives the analog PM carrier signal 916. In step 4610, theenergy transfer module 6304 receives the energy transfer signal 5406. Instep 4612, the energy transfer module 6304 transfers energy from theanalog PM carrier signal 916 at the aliasing rate of the energy transfersignal 5406, to down-convert the analog PM carrier signal 916 to the PMintermediate signal 5412.

Operation of the energy transfer system 6302 is now described for thedigital PM carrier signal 1016, with reference to the flowchart 4607 andthe timing diagrams in FIGS. 55A–G. In step 4608, the energy transfermodule 6304 receives the digital PM carrier signal 1016. In step 4610,the energy transfer module 6304 receives the energy transfer signal5506. In step 4612, the energy transfer module 6304 transfers energyfrom the digital PM carrier signal 1016 at the aliasing rate of theenergy transfer signal 5506, to down-convert the digital PM carriersignal 1016 to the PM intermediate signal 5512.

Example embodiments of the energy transfer module 6304 are disclosed inSections 4 and 5 below.

-   -   -   2.2.4 Other Embodiments

The embodiments described above are provided for purposes ofillustration. These embodiments are not intended to limit the invention.Alternate embodiments, differing slightly or substantially from thosedescribed herein, will be apparent to persons skilled in the relevantart(s) based on the teachings contained herein. Such alternateembodiments fall within the scope and spirit of the present invention.Example implementations of the energy transfer module 6304 are disclosedin Sections 4 and 5 below.

-   -   2.3 Implementation Examples

Exemplary operational and/or structural implementations related to themethod(s), structure(s), and/or embodiments described above arepresented in Sections 4 and 5 below. These implementations are presentedfor purposes of illustration, and not limitation. The invention is notlimited to the particular implementation examples described therein.Alternate implementations (including equivalents, extensions,variations, deviations, etc., of those described herein) will beapparent to persons skilled in the relevant art(s) based on theteachings contained herein. Such alternate implementations fall withinthe scope and spirit of the present invention.

3. Directly Down-Converting an EM Signal to an Demodulated BasebandSignal by Transferring Energy from the EM Signal

In an embodiment, the invention directly down-converts an EM signal to abaseband signal, by transferring energy from the EM signal. Thisembodiment is referred to herein as direct-to-data down-conversion andis illustrated by 4516 in FIG. 45B.

This embodiment can be implemented with modulated and unmodulated EMsignals. This embodiment is described herein using the modulated carriersignal F_(MC) in FIG. 1, as an example. In the example, the modulatedcarrier signal F_(MC) is directly down-converted to the demodulatedbaseband signal F_(DMB). Upon reading the disclosure and examplestherein, one skilled in the relevant art(s) will understand that theinvention can be implemented to down-convert any EM signal, includingbut not limited to, modulated carrier signals and unmodulated carriersignals.

The following sections describe methods for directly down-converting themodulated carrier signal F_(MC) to the demodulated baseband signalF_(DMB). Exemplary structural embodiments for implementing the methodsare also described. It should be understood that the invention is notlimited to the particular embodiments described below. Equivalents,extensions, variations, deviations, etc., of the following will beapparent to persons skilled in the relevant art(s) based on theteachings contained herein. Such equivalents, extensions, variations,deviations, etc., are within the scope and spirit of the presentinvention.

The following sections include a high level discussion, exampleembodiments, and implementation examples.

-   -   3.1 High Level Description

This section (including its subsections) provides a high-leveldescription of transferring energy from the modulated carrier signalF_(MC) to directly down-convert the modulated carrier signal F_(MC) tothe demodulated baseband signal F_(DMB), according to the invention. Inparticular, an operational process of directly down-converting themodulated carrier signal F_(MC) to the demodulated baseband signalF_(DMB) is described at a high-level. Also, a structural implementationfor implementing this process is described at a high-level. Thestructural implementation is described herein for illustrative purposes,and is not limiting. In particular, the process described in thissection can be achieved using any number of structural implementations,one of which is described in this section. The details of suchstructural implementations will be apparent to persons skilled in therelevant art(s) based on the teachings contained herein.

-   -   -   3.1.1 Operational Description

FIG. 46C depicts a flowchart 4613 that illustrates an exemplary methodfor transferring energy from the modulated carrier signal F_(MC) todirectly down-convert the modulated carrier signal F_(MC) to thedemodulated baseband signal F_(DMB). The exemplary method illustrated inthe flowchart 4613 is an embodiment of the flowchart 4601 in FIG. 46A.

Any and all combinations of modulation techniques are valid for thisinvention. For ease of discussion, the digital AM carrier signal 616 isused to illustrate a high level operational description of theinvention. Subsequent sections provide detailed flowcharts anddescriptions for AM and PM example embodiments. FM presents specialconsiderations that are dealt with separately in Section III.3. Uponreading the disclosure and examples therein, one skilled in the relevantart(s) will understand that the invention can be implemented todown-convert any type of EM signal, including any form of modulatedcarrier signal and unmodulated carrier signals.

The high-level process illustrated in the flowchart 4613 is nowdescribed at a high level using the digital AM carrier signal 616, fromFIG. 6C. The digital AM carrier signal 616 is re-illustrated in FIG. 56Afor convenience.

The process of the flowchart 4613 begins at step 4614, which includesreceiving an EM signal. Step 4613 is represented by the digital AMcarrier signal 616.

Step 4616 includes receiving an energy transfer signal having analiasing rate F_(AR). FIG. 56B illustrates an example energy transfersignal 5602, which includes a train of energy transfer pulses 5604having apertures 5606 that are optimized for energy transfer. Theoptimized apertures 5606 are non-negligible and tend away from zero.

The non-negligible apertures 5606 can be any width other than the periodof the EM signal, or a multiple thereof. For example, the non-negligibleapertures 5606 can be less than the period of the signal 616 such as, ⅛,¼, ½, ¾, etc., of the period of the signal 616. Alternatively, thenon-negligible apertures 5606 can be greater than the period of thesignal 616. The width and amplitude of the apertures 5606 can beoptimized based on one or more of a variety of criteria, as described insections below.

The energy transfer pulses 5604 repeat at the aliasing rate or pulserepetition rate. The aliasing rate is determined in accordance with EQ.(2), reproduced below for convenience.F _(C) =n·F _(AR) ±F _(IF)  EQ. (2)

When directly down-converting an EM signal to baseband (i.e., zero IF),EQ. (2) becomes:F _(C) =n·F _(AR)  EQ. (8)

Thus, to directly down-convert the AM signal 616 to a demodulatedbaseband signal, the aliasing rate is substantially equal to thefrequency of the AM signal 616 or to a harmonic or sub-harmonic thereof.Although the aliasing rate is too low to permit reconstruction of higherfrequency components of the AM signal 616 (i.e., the carrier frequency),it is high enough to permit substantial reconstruction of the lowerfrequency modulating baseband signal 310.

Step 4618 includes transferring energy from the EM signal at thealiasing rate to directly down-convert the EM signal to a demodulatedbaseband signal F_(DMB). FIG. 56C illustrates a demodulated basebandsignal 5610 that is generated by the direct down-conversion process. Thedemodulated baseband signal 5610 is similar to the digital modulatingbaseband signal 310 in FIG. 3.

FIG. 56D depicts a filtered demodulated baseband signal 5612, which canbe generated from the demodulated baseband signal 5610. The inventioncan thus generate a filtered output signal, a partially filtered outputsignal, or a relatively unfiltered output signal. The choice betweenfiltered, partially filtered and non-filtered output signals isgenerally a design choice that depends upon the application of theinvention.

-   -   -   3.1.2 Structural Description

In an embodiment, the energy transfer system 6302 transfers energy fromany type of EM signal, including modulated carrier signals andunmodulated carrier signal, to directly down-convert the EM signal to ademodulated baseband signal. Preferably, the energy transfer system 6302transfers energy from the EM signal 1304 to down-convert it todemodulated baseband signal in the manner shown in the operationalflowchart 4613. However, it should be understood that the scope andspirit of the invention includes other structural embodiments forperforming the steps of the flowchart 4613. The specifics of the otherstructural embodiments will be apparent to persons skilled in therelevant art(s) based on the discussion contained herein.

Operation of the energy transfer system 6302 is now described in at ahigh level for the digital AM carrier signal 616, with reference to theflowchart 4613 and the timing diagrams illustrated in FIGS. 56A–D. Instep 4614, the energy transfer module 6304 receives the digital AMcarrier signal 616. In step 4616, the energy transfer module 6304receives the energy transfer signal 5602. In step 4618, the energytransfer module 6304 transfers energy from the digital AM carrier signal616 at the aliasing rate to directly down-convert it to the demodulatedbaseband signal 5610.

Example implementations of the energy transfer module 6302 are disclosedin Sections 4 and 5 below.

-   -   3.2 Example Embodiments

Various embodiments related to the method(s) and structure(s) describedabove are presented in this section (and its subsections). Theseembodiments are described herein for purposes of illustration, and notlimitation. The invention is not limited to these embodiments. Alternateembodiments (including equivalents, extensions, variations, deviations,etc., of the embodiments described herein) will be apparent to personsskilled in the relevant art(s) based on the teachings contained herein.The invention is intended and adapted to include such alternateembodiments.

The method for down-converting the EM signal to the demodulated basebandsignal F_(DMB), illustrated in the flowchart 4613 of FIG. 46C, can beimplemented with various types of modulated carrier signals including,but not limited to, AM, PM, etc., or any combination thereof. Theflowchart 4613 of FIG. 46C is described below for AM and PM. Theexemplary descriptions below are intended to facilitate an understandingof the present invention. The present invention is not limited to or bythe exemplary embodiments below.

-   -   -   3.2.1 First Example Embodiment: Amplitude Modulation            -   3.2.1.1 Operational Description

Operation of the exemplary process of the flowchart 4613 in FIG. 46C isdescribed below for the analog AM carrier signal 516, illustrated inFIG. 5C, and for the digital AM carrier signal 616, illustrated in FIG.6C.

-   -   -   -   -   3.2.1.1.1 Analog AM Carrier Signal

A process for directly down-converting the analog AM carrier signal 516in FIG. 5C to a demodulated baseband signal is now described withreference to the flowchart 4613 in FIG. 46C. The analog AM carriersignal 516 is re-illustrated in 57A for convenience. For this example,the analog AM carrier signal 516 oscillates at approximately 900 MHZ. InFIG. 57B, an analog AM carrier signal portion 5704 illustrates a portionof the analog AM carrier signal 516 on an expanded time scale.

The process begins at step 4614, which includes receiving an EM signal.This is represented by the analog AM carrier signal 516.

Step 4616 includes receiving an energy transfer signal having analiasing rate F_(AR). In FIG. 57C, an example energy transfer signal5706 is illustrated on approximately the same time scale as FIG. 57B.The energy transfer signal 5706 includes a train of energy transferpulses 5707 having non-negligible apertures that tend away from zerotime in duration. The energy transfer pulses 5707 repeat at the aliasingrate, which is determined or selected as previously described.Generally, when down-converting an EM signal to a demodulated basebandsignal, the aliasing rate F_(AR) is substantially equal to a harmonicor, more typically, a sub-harmonic of the EM signal.

Step 4618 includes transferring energy from the EM signal at thealiasing rate to directly down-convert the EM signal to the demodulatedbaseband signal F_(DMB). In FIG. 57D, an affected analog AM carriersignal 5708 illustrates effects of transferring energy from the analogAM carrier signal 516 at the aliasing rate F_(AR). The affected analogAM carrier signal 5708 is illustrated on substantially the same timescale as FIGS. 57B and 57C.

FIG. 57E illustrates a demodulated baseband signal 5712, which isgenerated by the down-conversion process. Because a harmonic of thealiasing rate is substantially equal to the frequency of the signal 516,essentially no IF is produced. The only substantial aliased component isthe baseband signal. The demodulated baseband signal 5712 is illustratedwith an arbitrary load impedance. Load impedance optimizations arediscussed in Section 5 below.

The demodulated baseband signal 5712 includes portions 5710A, whichcorrelate with the energy transfer pulses 5707 in FIG. 57C, and portions5710B, which are between the energy transfer pulses 5707. Portions 5710Arepresent energy transferred from the analog AM carrier signal 516 to astorage device, while simultaneously driving an output load. Theportions 5710A occur when a switching module is closed by the energytransfer pulses 5707. Portions 5710B represent energy stored in astorage device continuing to drive the load. Portions 5710B occur whenthe switching module is opened after energy transfer pulses 5707.

In FIG. 57F, a demodulated baseband signal 5716 represents a filteredversion of the demodulated baseband signal 5712, on a compressed timescale. The demodulated baseband signal 5716 is substantially similar tothe modulating baseband signal 210 and can be further processed usingany signal processing technique(s) without further down-conversion ordemodulation.

The present invention can output the unfiltered demodulated basebandsignal 5712, the filtered demodulated baseband signal 5716, a partiallyfiltered demodulated baseband signal, a stair step output signal, etc.The choice between these embodiments is generally a design choice thatdepends upon the application of the invention.

The aliasing rate of the energy transfer signal is preferably controlledto optimize the demodulated baseband signal for amplitude output andpolarity, as desired.

The drawings referred to herein illustrate direct down-conversion inaccordance with the invention. For example, the demodulated basebandsignals 5712 in FIGS. 57E and 5716 in FIG. 57F illustrate that theanalog AM carrier signal 516 was directly down-converted to ademodulated baseband signal by retaining enough baseband information forsufficient reconstruction.

-   -   -   -   -   3.2.1.1.2 Digital AM Carrier Signal

A process for directly down-converting the digital AM carrier signal 616in FIG. 6C to a demodulated baseband signal is now described for theflowchart 4613 in FIG. 46C. The digital AM carrier signal 616 isre-illustrated in 58A for convenience. For this example, the digital AMcarrier signal 616 oscillates at approximately 900 MHZ. In FIG. 58B, adigital AM carrier signal portion 5804 illustrates a portion of thedigital AM carrier signal 616 on an expanded time scale.

The process begins at step 4614, which includes receiving an EM signal.This is represented by the digital AM carrier signal 616.

Step 4616 includes receiving an energy transfer signal having analiasing rate F_(AR). In FIG. 58C, an example energy transfer signal5806 is illustrated on approximately the same time scale as FIG. 58B.The energy transfer signal 5806 includes a train of energy transferpulses 5807 having non-negligible apertures that tend away from zerotime in duration. The energy transfer pulses 5807 repeat at the aliasingrate, which is determined or selected as previously described.Generally, when directly down-converting an EM signal to a demodulatedbaseband signal, the aliasing rate F_(AR) is substantially equal to aharmonic or, more typically, a sub-harmonic of the EM signal.

Step 4618 includes transferring energy from the EM signal at thealiasing rate to directly down-convert the EM signal to the demodulatedbaseband signal F_(DMB). In FIG. 58D, an affected digital AM carriersignal 5808 illustrates effects of transferring energy from the digitalAM carrier signal 616 at the aliasing rate F_(AR). The affected digitalAM carrier signal 5808 is illustrated on substantially the same timescale as FIGS. 58B and 58C.

FIG. 58E illustrates a demodulated baseband signal 5812, which isgenerated by the down-conversion process. Because a harmonic of thealiasing rate is substantially equal to the frequency of the signal 616,essentially no IF is produced. The only substantial aliased component isthe baseband signal. The demodulated baseband signal 5812 is illustratedwith an arbitrary load impedance. Load impedance optimizations arediscussed in Section 5 below.

The demodulated baseband signal 5812 includes portions 5810A, whichcorrelate with the energy transfer pulses 5807 in FIG. 58C, and portions5810B, which are between the energy transfer pulses 5807. Portions 5810Arepresent energy transferred from the digital AM carrier signal 616 to astorage device, while simultaneously driving an output load. Theportions 5810A occur when a switching module is closed by the energytransfer pulses 5807. Portions 5810B represent energy stored in astorage device continuing to drive the load. Portions 5810B occur whenthe switching module is opened after energy transfer pulses 5807.

In FIG. 58F, a demodulated baseband signal 5816 represents a filteredversion of the demodulated baseband signal 5812, on a compressed timescale. The demodulated baseband signal 5816 is substantially similar tothe modulating baseband signal 310 and can be further processed usingany signal processing technique(s) without further down-conversion ordemodulation.

The present invention can output the unfiltered demodulated basebandsignal 5812, the filtered demodulated baseband signal 5816, a partiallyfiltered demodulated baseband signal, a stair step output signal, etc.The choice between these embodiments is generally a design choice thatdepends upon the application of the invention.

The aliasing rate of the energy transfer signal is preferably controlledto optimize the down-converted signal for amplitude output and polarity,as desired.

The drawings referred to herein illustrate direct down-conversion inaccordance with the invention. For example, the demodulated basebandsignals 5812 in FIGS. 58E and 5816 in FIG. 58F illustrate that thedigital AM carrier signal 616 was directly down-converted to ademodulated baseband signal by retaining enough baseband information forsufficient reconstruction.

-   -   -   -   3.2.1.2 Structural Description

In an embodiment, the energy transfer module 6304 preferably transfersenergy from the EM signal to directly down-convert it to a demodulatedbaseband signal in the manner shown in the operational flowchart 4613.But it should be understood that the scope and spirit of the inventionincludes other structural embodiments for performing the steps of theflowchart 1413. The specifics of the other structural embodiments willbe apparent to persons skilled in the relevant art(s) based on thediscussion contained herein.

Operation of the energy transfer system 6302 is now described for thedigital AM carrier signal 516, with reference to the flowchart 4613 andthe timing diagrams in FIGS. 57A–F. In step 4612, the energy transfermodule 6404 receives the analog AM carrier signal 516. In step 4614, theenergy transfer module 6404 receives the energy transfer signal 5706. Instep 4618, the energy transfer module 6404 transfers energy from theanalog AM carrier signal 516 at the aliasing rate of the energy transfersignal 5706, to directly down-convert the digital AM carrier signal 516to the demodulated baseband signals 5712 or 5716.

The operation of the energy transfer system 6402 is now described forthe digital AM carrier signal 616, with reference to the flowchart 4613and the timing diagrams in FIGS. 58A–F. In step 4614, the energytransfer module 6404 receives the digital AM carrier signal 616. In step4616, the energy transfer module 6404 receives the energy transfersignal 5806. In step 4618, the energy transfer module 6404 transfersenergy from the digital AM carrier signal 616 at the aliasing rate ofthe energy transfer signal 5806, to directly down-convert the digital AMcarrier signal 616 to the demodulated baseband signals 5812 or 5816.

Example implementations of the energy transfer module 6302 are disclosedin Sections 4 and 5 below.

-   -   -   3.2.2 Second Example Embodiment: Phase Modulation            -   3.2.2.1 Operational Description

Operation of the exemplary process of flowchart 4613 in FIG. 46C isdescribed below for the analog PM carrier signal 916, illustrated inFIG. 9C and for the digital PM carrier signal 1016, illustrated in FIG.10C.

-   -   -   -   -   3.2.2.1.1 Analog PM Carrier Signal

A process for directly down-converting the analog PM carrier signal 916to a demodulated baseband signal is now described for the flowchart 4613in FIG. 46C. The analog PM carrier signal 916 is re-illustrated in 59Afor convenience. For this example, the analog PM carrier signal 916oscillates at approximately 900 MHZ. In FIG. 59B, an analog PM carriersignal portion 5904 illustrates a portion of the analog PM carriersignal 916 on an expanded time scale.

The process begins at step 4614, which includes receiving an EM signal.This is represented by the analog PM carrier signal 916.

Step 4616 includes receiving an energy transfer signal having analiasing rate F_(AR). In FIG. 59C, an example energy transfer signal5906 is illustrated on approximately the same time scale as FIG. 59B.The energy transfer signal 5906 includes a train of energy transferpulses 5907 having non-negligible apertures that tend away from zerotime in duration. The energy transfer pulses 5907 repeat at the aliasingrate, which is determined or selected as previously described.Generally, when directly down-converting an EM signal to a demodulatedbaseband signal, the aliasing rate F_(AR) is substantially equal to aharmonic or, more typically, a sub-harmonic of the EM signal.

Step 4618 includes transferring energy from the EM signal at thealiasing rate to directly down-convert the EM signal to the demodulatedbaseband signal F_(DMB). In FIG. 59D, an affected analog PM carriersignal 5908 illustrates effects of transferring energy from the analogPM carrier signal 916 at the aliasing rate F_(AR). The affected analogPM carrier signal 5908 is illustrated on substantially the same timescale as FIGS. 59B and 59C.

FIG. 59E illustrates a demodulated baseband signal 5912, which isgenerated by the down-conversion process. Because a harmonic of thealiasing rate is substantially equal to the frequency of the signal 516,essentially no IF is produced. The only substantial aliased component isthe baseband signal. The demodulated baseband signal 5912 is illustratedwith an arbitrary load impedance. Load impedance optimizations arediscussed in Section 5 below.

The demodulated baseband signal 5912 includes portions 5910A, whichcorrelate with the energy transfer pulses 5907 in FIG. 59C, and portions5910B, which are between the energy transfer pulses 5907. Portions 5910Arepresent energy transferred from the analog PM carrier signal 916 to astorage device, while simultaneously driving an output load. Theportions 5910A occur when a switching module is closed by the energytransfer pulses 5907. Portions 5910B represent energy stored in astorage device continuing to drive the load. Portions 5910B occur whenthe switching module is opened after energy transfer pulses 5907.

In FIG. 59F, a demodulated baseband signal 5916 represents a filteredversion of the demodulated baseband signal 5912, on a compressed timescale. The demodulated baseband signal 5916 is substantially similar tothe modulating baseband signal 210 and can be further processed usingany signal processing technique(s) without further down-conversion ordemodulation.

The present invention can output the unfiltered demodulated baseband5912, the filtered demodulated baseband signal 5916, a partiallyfiltered demodulated baseband signal, a stair step output signal, etc.The choice between these embodiments is generally a design choice thatdepends upon the application of the invention.

The aliasing rate of the energy transfer signal is preferably controlledto optimize the down-converted signal for amplitude output and polarity,as desired.

The drawings referred to herein illustrate direct down-conversion inaccordance with the invention. For example, the demodulated basebandsignals 5912 in FIGS. 59E and 5916 in FIG. 59F illustrate that theanalog PM carrier signal 916 was successfully down-converted to ademodulated baseband signal by retaining enough baseband information forsufficient reconstruction.

-   -   -   -   -   3.2.2.1.2 Digital PM Carrier Signal

A process for directly down-converting the digital PM carrier signal1016 in FIG. 6C to a demodulated baseband signal is now described forthe flowchart 4613 in FIG. 46C. The digital PM carrier signal 1016 isre-illustrated in 60A for convenience. For this example, the digital PMcarrier signal 1016 oscillates at approximately 900 MHZ. In FIG. 60B, adigital PM carrier signal portion 6004 illustrates a portion of thedigital PM carrier signal 1016 on an expanded time scale.

The process begins at step 4614, which includes receiving an EM signal.This is represented by the digital PM carrier signal 1016.

Step 4616 includes receiving an energy transfer signal F_(AR). In FIG.60C, an example energy transfer signal 6006 is illustrated onapproximately the same time scale as FIG. 60B. The energy transfersignal 6006 includes a train of energy transfer pulses 6007 havingnon-negligible apertures that tend away from zero time in duration. Theenergy transfer pulses 6007 repeat at the aliasing rate, which isdetermined or selected as previously described. Generally, when directlydown-converting an EM signal to a demodulated baseband signal, thealiasing rate F_(AR) is substantially equal to a harmonic or, moretypically, a sub-harmonic of the EM signal.

Step 4618 includes transferring energy from the EM signal at thealiasing rate to directly down-convert the EM signal to the demodulatedbaseband signal F_(DMB). In FIG. 60D, an affected digital PM carriersignal 6008 illustrates effects of transferring energy from the digitalPM carrier signal 1016 at the aliasing rate F_(AR). The affected digitalPM carrier signal 6008 is illustrated on substantially the same timescale as FIGS. 60B and 60C.

FIG. 60E illustrates a demodulated baseband signal 6012, which isgenerated by the down-conversion process. Because a harmonic of thealiasing rate is substantially equal to the frequency of the signal1016, essentially no IF is produced. The only substantial aliasedcomponent is the baseband signal. The demodulated baseband signal 6012is illustrated with an arbitrary load impedance. Load impedanceoptimizations are discussed in Section 5 below.

The demodulated baseband signal 6012 includes portions 6010A, whichcorrelate with the energy transfer pulses 6007 in FIG. 60C, and portions6010B, which are between the energy transfer pulses 6007. Portions 6010Arepresent energy transferred from the digital PM carrier signal 1016 toa storage device, while simultaneously driving an output load. Theportions 6010A occur when a switching module is closed by the energytransfer pulses 6007. Portions 6010B represent energy stored in astorage device continuing to drive the load. Portions 6010B occur whenthe switching module is opened after energy transfer pulses 6007.

In FIG. 60F, a demodulated baseband signal 6016 represents a filteredversion of the demodulated baseband signal 6012, on a compressed timescale. The demodulated baseband signal 6016 is substantially similar tothe modulating baseband signal 310 and can be further processed usingany signal processing technique(s) without further down-conversion ordemodulation.

The present invention can output the unfiltered demodulated basebandsignal 6012, the filtered demodulated baseband signal 6016, a partiallyfiltered demodulated baseband signal, a stair step output signal, etc.The choice between these embodiments is generally a design choice thatdepends upon the application of the invention.

The aliasing rate of the energy transfer signal is preferably controlledto optimize the down-converted signal for amplitude output and polarity,as desired.

The drawings referred to herein illustrate direct down-conversion inaccordance with the invention. For example, the demodulated basebandsignals 6012 in FIGS. 60E and 6016 in FIG. 60F illustrate that thedigital PM carrier signal 1016 was successfully down-converted to ademodulated baseband signal by retaining enough baseband information forsufficient reconstruction.

-   -   -   -   3.2.2.2 Structural Description

In an embodiment, the energy transfer system 6302 preferably transfersenergy from an EM signal to directly down-convert it to a demodulatedbaseband signal in the manner shown in the operational flowchart 4613.But it should be understood that the scope and spirit of the inventionincludes other structural embodiments for performing the steps of theflowchart 1413. The specifics of the other structural embodiments willbe apparent to persons skilled in the relevant art(s) based on thediscussion contained herein.

Operation of the energy transfer system 6302 is now described for theanalog PM carrier signal 916, with reference to the flowchart 4613 andthe timing diagrams in FIGS. 59A–F. In step 4614, the energy transfermodule 6304 receives the analog PM carrier signal 916. In step 4616, theenergy transfer module 6304 receives the energy transfer signal 5906. Instep 4618, the energy transfer module 6304 transfers energy from theanalog PM carrier signal 916 at the aliasing rate of the energy transfersignal 5906, to directly down-convert the analog PM carrier signal 916to the demodulated baseband signals 5912 or 5916.

Operation of the energy transfer system 6302 is now described for thedigital PM carrier signal 1016, with reference to the flowchart 4613 andto the timing diagrams in FIGS. 60A–F. In step 4614, the energy transfermodule 6404 receives the digital PM carrier signal 1016. In step 4616,the energy transfer module 6404 receives the energy transfer signal6006. In step 4618, the energy transfer module 6404 transfers energyfrom the digital PM carrier signal 1016 at the aliasing rate of theenergy transfer signal 6006, to directly down-convert the digital PMcarrier signal 1016 to the demodulated baseband signal 6012 or 6016.

Example implementations of the energy transfer module 6302 are disclosedin Sections 4 and 5 below.

-   -   -   3.2.3 Other Embodiments

The embodiments described above are provided for purposes ofillustration. These embodiments are not intended to limit the invention.Alternate embodiments, differing slightly or substantially from thosedescribed herein, will be apparent to persons skilled in the relevantart(s) based on the teachings contained herein. Such alternateembodiments fall within the scope and spirit of the present invention.Example implementations of the energy transfer module 6302 are disclosedin Sections 4 and 5 below.

-   -   3.3 Implementation Examples

Exemplary operational and/or structural implementations related to themethod(s), structure(s), and/or embodiments described above arepresented in Sections 4 and 5 below. These implementations are presentedfor purposes of illustration, and not limitation. The invention is notlimited to the particular implementation examples described therein.Alternate implementations (including equivalents, extensions,variations, deviations, etc., of those described herein) will beapparent to persons skilled in the relevant art(s) based on theteachings contained herein. Such alternate implementations fall withinthe scope and spirit of the present invention.

4. Modulation Conversion

In an embodiment, the invention down-converts an FM carrier signalF_(FMC) to a non-FM signal F_((NON-FM)), by transferring energy from theFM carrier signal F_(FMC) at an aliasing rate. This embodiment isillustrated in FIG. 45B as 4518.

In an example embodiment, the FM carrier signal F_(FMC) isdown-converted to a phase modulated (PM) signal F_(PM). In anotherexample embodiment, the FM carrier signal F_(FMC) is down-converted toan amplitude modulated (AM) signal F_(AM). The down-converted signal canbe demodulated with any conventional demodulation technique to obtain ademodulated baseband signal F_(DMB).

The invention can be implemented with any type of FM signal. Exemplaryembodiments are provided below for down-converting a frequency shiftkeying (FSK) signal to a non-FSK signal. FSK is a sub-set of FM, whereinan FM signal shifts or switches between two or more frequencies. FSK istypically used for digital modulating baseband signals, such as thedigital modulating baseband signal 310 in FIG. 3. For example, in FIG.8, the digital FM signal 816 is an FSK signal that shifts between anupper frequency and a lower frequency, corresponding to amplitude shiftsin the digital modulating baseband signal 310. The FSK signal 816 isused in example embodiments below.

In a first example embodiment, energy is transferred from the FSK signal816 at an aliasing rate that is based on a mid-point between the upperand lower frequencies of the FSK signal 816. When the aliasing rate isbased on the mid-point, the FSK signal 816 is down-converted to a phaseshift keying (PSK) signal. PSK is a sub-set of phase modulation, whereina PM signal shifts or switches between two or more phases. PSK istypically used for digital modulating baseband signals. For example, inFIG. 10, the digital PM signal 1016 is a PSK signal that shifts betweentwo phases. The PSK signal 1016 can be demodulated by any conventionalPSK demodulation technique(s).

In a second example embodiment, energy is transferred from the FSKsignal 816 at an aliasing rate that is based upon either the upperfrequency or the lower frequency of the FSK signal 816. When thealiasing rate is based upon the upper frequency or the lower frequencyof the FSK signal 816, the FSK signal 816 is down-converted to anamplitude shift keying (ASK) signal. ASK is a sub-set of amplitudemodulation, wherein an AM signal shifts or switches between two or moreamplitudes. ASK is typically used for digital modulating basebandsignals. For example, in FIG. 6, the digital AM signal 616 is an ASKsignal that shifts between the first amplitude and the second amplitude.The ASK signal 616 can be demodulated by any conventional ASKdemodulation technique(s).

The following sections describe methods for transferring energy from anFM carrier signal F_(FMC) to down-convert it to the non-FM signalF_((NON-FM)). Exemplary structural embodiments for implementing themethods are also described. It should be understood that the inventionis not limited to the particular embodiments described below.Equivalents, extensions, variations, deviations, etc., of the followingwill be apparent to persons skilled in the relevant art(s) based on theteachings contained herein. Such equivalents, extensions, variations,deviations, etc., are within the scope and spirit of the presentinvention.

The following sections include a high level discussion, exampleembodiments, and implementation examples.

-   -   4.1 High Level Description

This section (including its subsections) provides a high-leveldescription of transferring energy from the FM carrier signal F_(FM) todown-convert it to the non-FM signal F_((NON-FM)), according to theinvention. In particular, an operational process for down-converting theFM carrier signal F_(Fm) to the non-FM signal F_((NON-FM)) is describedat a high-level. Also, a structural implementation for implementing thisprocess is described at a high-level. The structural implementation isdescribed herein for illustrative purposes, and is not limiting. Inparticular, the process described in this section can be achieved usingany number of structural implementations, one of which is described inthis section. The details of such structural implementations will beapparent to persons skilled in the relevant art(s) based on theteachings contained herein.

-   -   -   4.1.1 Operational Description

FIG. 46D depicts a flowchart 4619 that illustrates an exemplary methodfor down-converting the FM carrier signal F_(FMC) to the non-FM signalF_((NON-FM)). The exemplary method illustrated in the flowchart 4619 isan embodiment of the flowchart 4601 in FIG. 46A.

Any and all forms of frequency modulation techniques are valid for thisinvention. For ease of discussion, the digital FM carrier (FSK) signal816 is used to illustrate a high level operational description of theinvention. Subsequent sections provide detailed flowcharts anddescriptions for the FSK signal 816. Upon reading the disclosure andexamples therein, one skilled in the relevant art(s) will understandthat the invention can be implemented to down-convert any type of FMsignal.

The method illustrated in the flowchart 4619 is described below at ahigh level for down-converting the FSK signal 816 in FIG. 8C to a PSKsignal. The FSK signal 816 is re-illustrated in FIG. 84A forconvenience.

The process of the flowchart 4619 begins at step 4620, which includesreceiving an FM signal. This is represented by the FSK signal 816. TheFSK signal 816 shifts between a first frequency 8410 and a secondfrequency 8412. The first frequency 8410 can be higher or lower than thesecond frequency 8412. In an exemplary embodiment, the first frequency8410 is approximately 899 MHZ and the second frequency 8412 isapproximately 901 MHZ.

Step 4622 includes receiving an energy transfer signal having analiasing rate F_(AR). FIG. 84B illustrates an example energy transfersignal 8402 which includes a train of energy transfer pulses 8403 havingnon-negligible apertures 8405 that tend away from zero time in duration.

The energy transfer pulses 8403 repeat at the aliasing rate F_(AR),which is determined or selected as previously described. Generally, whendown-converting an FM carrier signal F_(FMC) to a non-FM signalF_((NON-FM)), the aliasing rate is substantially equal to a harmonic or,more typically, a sub-harmonic of a frequency within the FM signal. Inthis example overview embodiment, where the FSK signal 816 is to bedown-converted to a PSK signal, the aliasing rate is substantially equalto a harmonic or, more typically, a sub-harmonic of the mid-pointbetween the first frequency 8410 and the second frequency 8412. For thepresent example, the mid-point is approximately 900 MHZ.

Step 4624 includes transferring energy from the FM carrier signalF_(FMC) at the aliasing rate to down-convert the FM carrier signalF_(FMC) to the non-FM signal F_((NON-FM)). FIG. 84C illustrates a PSKsignal 8404, which is generated by the modulation conversion process.

When the second frequency 8412 is under-sampled, the PSK signal 8404 hasa frequency of approximately 1 MHZ and is used as a phase reference.When the first frequency 8410 is under-sampled, the PSK signal 8404 hasa frequency of 1 MHZ and is phase shifted 180 degrees from the phasereference.

FIG. 84D depicts a PSK signal 8406, which is a filtered version of thePSK signal 8404. The invention can thus generate a filtered outputsignal, a partially filtered output signal, or a relatively unfilteredstair step output signal. The choice between filtered, partiallyfiltered and non-filtered output signals is generally a design choicethat depends upon the application of the invention.

The aliasing rate of the energy transfer signal is preferably controlledto optimize the down-converted signal for amplitude output and polarity,as desired.

Detailed exemplary embodiments for down-converting an FSK signal to aPSK signal and for down-converting an FSK signal to an ASK signal areprovided below.

-   -   -   4.1.2 Structural Description

FIG. 63 illustrates the energy transfer system 6302 according to anembodiment of the invention. The energy transfer system 6302 includesthe energy transfer module 6304. The energy transfer system 6302 is anexample embodiment of the generic aliasing system 1302 in FIG. 13.

In a modulation conversion embodiment, the EM signal 1304 is an FMcarrier signal F_(FMC) and the energy transfer module 6304 transfersenergy from FM carrier signal at a harmonic or, more typically, asub-harmonic of a frequency within the FM frequency band. Preferably,the energy transfer module 6304 transfers energy from the FM carriersignal F_(FMC) to down-convert it to a non-FM signal F_((NON-FM)) in themanner shown in the operational flowchart 4619. But it should beunderstood that the scope and spirit of the invention includes otherstructural embodiments for performing the steps of the flowchart 4619.The specifics of the other structural embodiments will be apparent topersons skilled in the relevant art(s) based on the discussion containedherein.

The operation of the energy transfer system 6302 shall now be describedwith reference to the flowchart 4619 and the timing diagrams of FIGS.84A–84D. In step 4620, the energy transfer module 6304 receives the FSKsignal 816. In step 4622, the energy transfer module 6304 receives theenergy transfer signal 8402. In step 4624, the energy transfer module6304 transfers energy from the FSK signal 816 at the aliasing rate ofthe energy transfer signal 8402 to down-convert the FSK signal 816 tothe PSK signal 8404 or 8406.

Example implementations of the energy transfer module 6302 are providedin Section 4 below.

-   -   4.2 Example Embodiments

Various embodiments related to the method(s) and structure(s) describedabove are presented in this section (and its subsections). Theseembodiments are described herein for purposes of illustration, and notlimitation. The invention is not limited to these embodiments. Alternateembodiments (including equivalents, extensions, variations, deviations,etc., of the embodiments described herein) will be apparent to personsskilled in the relevant art(s) based on the teachings contained herein.The invention is intended and adapted to include such alternateembodiments.

The method for down-converting an FM carrier signal F_(FMC) to a non-FMsignal, F_((NON-FM)), illustrated in the flowchart 4619 of FIG. 46D, canbe implemented with any type of FM carrier signal including, but notlimited to, FSK signals. The flowchart 4619 is described in detail belowfor down-converting an FSK signal to a PSK signal and fordown-converting a PSK signal to an ASK signal. The exemplarydescriptions below are intended to facilitate an understanding of thepresent invention. The present invention is not limited to or by theexemplary embodiments below.

-   -   -   4.2.1 First Example Embodiment: Down-Converting an FM Signal            to a PM Signal            -   4.2.1.1 Operational Description

A process for down-converting the FSK signal 816 in FIG. 8C to a PSKsignal is now described for the flowchart 4619 in FIG. 46D.

The FSK signal 816 is re-illustrated in FIG. 61A for convenience. TheFSK signal 816 shifts between a first frequency 6106 and a secondfrequency 6108. In the exemplary embodiment, the first frequency 6106 islower than the second frequency 6108. In an alternative embodiment, thefirst frequency 6106 is higher than the second frequency 6108. For thisexample, the first frequency 6106 is approximately 899 MHZ and thesecond frequency 6108 is approximately 901 MHZ.

FIG. 61B illustrates an FSK signal portion 6104 that represents aportion of the FSK signal 816 on an expanded time scale.

The process begins at step 4620, which includes receiving an FM signal.This is represented by the FSK signal 816.

Step 4622 includes receiving an energy transfer signal having analiasing rate F_(AR). FIG. 61C illustrates an example energy transfersignal 6107 on approximately the same time scale as FIG. 61B. The energytransfer signal 6107 includes a train of energy transfer pulses 6109having non-negligible apertures that tend away from zero time induration. The energy transfer pulses 6109 repeat at the aliasing rateF_(AR), which is determined or selected as described above. Generally,when down-converting an FM signal to a non-FM signal, the aliasing rateis substantially equal to a harmonic or, more typically, a sub-harmonicof a frequency within the FM signal.

In this example, where an FSK signal is being down-converted to a PSKsignal, the aliasing rate is substantially equal to a harmonic or, moretypically, a sub-harmonic, of the mid-point between the frequencies 6106and 6108. In this example, where the first frequency 6106 is 899 MHZ andsecond frequency 6108 is 901 MHZ, the mid-point is approximately 900MHZ. Suitable aliasing rates thus include 1.8 GHZ, 900 MHZ, 450 MHZ,etc.

Step 4624 includes transferring energy from the FM signal at thealiasing rate to down-convert it to the non-FM signal F_((NON-FM)). InFIG. 61D, an affected FSK signal 6118 illustrates effects oftransferring energy from the FSK signal 816 at the aliasing rate F_(AR).The affected FSK signal 6118 is illustrated on substantially the sametime scale as FIGS. 61B and 61C.

FIG. 61E illustrates a PSK signal 6112, which is generated by themodulation conversion process. PSK signal 6112 is illustrated with anarbitrary load impedance. Load impedance optimizations are discussed inSection 5 below.

The PSK signal 6112 includes portions 6110A, which correlate with theenergy transfer pulses 6107 in FIG. 61C. The PSK signal 6112 alsoincludes portions 6110B, which are between the energy transfer pulses6109. Portions 6110A represent energy transferred from the FSK 816 to astorage device, while simultaneously driving an output load. Theportions 6110A occur when a switching module is closed by the energytransfer pulses 6109. Portions 6110B represent energy stored in astorage device continuing to drive the load. Portions 6110B occur whenthe switching module is opened after energy transfer pulses 6107.

In FIG. 61F, a PSK signal 6114 represents a filtered version of the PSKsignal 6112, on a compressed time scale. The present invention canoutput the unfiltered demodulated baseband signal 6112, the filtereddemodulated baseband signal 6114, a partially filtered demodulatedbaseband signal, a stair step output signal, etc. The choice betweenthese embodiments is generally a design choice that depends upon theapplication of the invention. The PSK signals 6112 and 6114 can bedemodulated with a conventional demodulation technique(s).

The aliasing rate of the energy transfer signal is preferably controlledto optimize the down-converted signal for amplitude output and polarity,as desired.

The drawings referred to herein illustrate modulation conversion inaccordance with the invention. For example, the PSK signals 6112 inFIGS. 61E and 6114 in FIG. 61F illustrate that the FSK signal 816 wassuccessfully down-converted to a PSK signal by retaining enough basebandinformation for sufficient reconstruction.

-   -   -   -   4.2.1.2 Structural Description

The operation of the energy transfer system 1602 is now described fordown-converting the FSK signal 816 to a PSK signal, with reference tothe flowchart 4619 and to the timing diagrams of FIGS. 61A–E. In step4620, the energy transfer module 1606 receives the FSK signal 816 (FIG.61A). In step 4622, the energy transfer module 1606 receives the energytransfer signal 6107 (FIG. 61C). In step 4624, the energy transfermodule 1606 transfers energy from the FSK signal 816 at the aliasingrate of the energy transfer signal 6107 to down-convert the FSK signal816 to the PSK signal 6112 in FIG. 61E or the PSK signal 6114 in FIG.61F.

-   -   -   4.2.2 Second Example Embodiment: Down-Converting an FM            Signal to an AM Signal            -   4.2.2.1 Operational Description

A process for down-converting the FSK signal 816 in FIG. 8C to an ASKsignal is now described for the flowchart 4619 in FIG. 46D.

The FSK signal 816 is re-illustrated in FIG. 62A for convenience. TheFSK signal 816 shifts between a first frequency 6206 and a secondfrequency 6208. In the exemplary embodiment, the first frequency 6206 islower than the second frequency 6208. In an alternative embodiment, thefirst frequency 6206 is higher than the second frequency 6208. For thisexample, the first frequency 6206 is approximately 899 MHZ and thesecond frequency 6208 is approximately 901 MHZ.

FIG. 62B illustrates an FSK signal portion 6204 that represents aportion of the FSK signal 816 on an expanded time scale.

The process begins at step 4620, which includes receiving an FM signal.This is represented by the FSK signal 816.

Step 4622 includes receiving an energy transfer signal having analiasing rate F_(AR). FIG. 62C illustrates an example energy transfersignal 6207 on approximately the same time scale as FIG. 62B. The energytransfer signal 6207 includes a train of energy transfer pulses 6209having non-negligible apertures that tend away from zero time induration. The energy transfer pulses 6209 repeat at the aliasing rateF_(AR), which is determined or selected as described above. Generally,when down-converting an FM signal to a non-FM signal, the aliasing rateis substantially equal to a harmonic or, more typically, a sub-harmonicof a frequency within the FM signal.

In this example, where an FSK signal is being down-converted to an ASKsignal, the aliasing rate is substantially equal to a harmonic or, moretypically, a sub-harmonic, of either the first frequency 6206 or thesecond frequency 6208. In this example, where the first frequency 6206is 899 MHZ and the second frequency 6208 is 901 MHZ, the aliasing ratecan be substantially equal to a harmonic or sub-harmonic of 899 MHZ or901 MHZ.

Step 4624 includes transferring energy from the FM signal at thealiasing rate to down-convert it to the non-FM signal F_((NON-FM)). InFIG. 62D, an affected FSK signal 6218 illustrates effects oftransferring energy from the FSK signal 816 at the aliasing rate F_(AR).The affected FSK signal 6218 is illustrated on substantially the sametime scale as FIGS. 62B and 62C.

FIG. 62E illustrates an ASK signal 6212, which is generated by themodulation conversion process. ASK signal 6212 is illustrated with anarbitrary load impedance. Load impedance optimizations are discussed inSection 5 below.

The ASK signal 6212 includes portions 6210A, which correlate with theenergy transfer pulses 6209 in FIG. 62C. The ASK signal 6212 alsoincludes portions 6210B, which are between the energy transfer pulses6209. Portions 6210A represent energy transferred from the FSK 816 to astorage device, while simultaneously driving an output load. Portions6210A occur when a switching module is closed by the energy transferpulses 6207. Portions 6210B represent energy stored in a storage devicecontinuing to drive the load. Portions 6210B occur when the switchingmodule is opened after energy transfer pulses 6207.

In FIG. 62F, an ASK signal 6214 represents a filtered version of the ASKsignal 6212, on a compressed time scale. The present invention canoutput the unfiltered demodulated baseband signal 6212, the filtereddemodulated baseband signal 6214, a partially filtered demodulatedbaseband signal, a stair step output signal, etc. The choice betweenthese embodiments is generally a design choice that depends upon theapplication of the invention. The ASK signals 6212 and 6214 can bedemodulated with a conventional demodulation technique(s).

The aliasing rate of the energy transfer signal is preferably controlledto optimize the down-converted signal for amplitude output and/orpolarity, as desired.

The drawings referred to herein illustrate modulation conversion inaccordance with the invention. For example, the ASK signals 6212 inFIGS. 62E and 6214 in FIG. 62F illustrate that the FSK signal 816 wassuccessfully down-converted to an ASK signal by retaining enoughbaseband information for sufficient reconstruction.

-   -   -   -   4.2.2.2 Structural Description

The operation of the energy transfer system 1602 is now described fordown-converting the FSK signal 816 to an ASK signal, with reference tothe flowchart 4619 and to the timing diagrams of FIGS. 62A–F. In step4620, the energy transfer module 6304 receives the FSK signal 816 (FIG.62A). In step 4622, the energy transfer module 6304 receives the energytransfer signal 6207 (FIG. 62C). In step 4624, the energy transfermodule 6304 transfers energy from the FSK signal 818 at the aliasingrate of the energy transfer signal 6207 to down-convert the FSK signal816 to the ASK signal 6212 in FIG. 62E or the ASK signal 6214 in FIG.62F.

-   -   -   4.2.3 Other Example Embodiments

The embodiments described above are provided for purposes ofillustration. These embodiments are not intended to limit the invention.Alternate embodiments, differing slightly or substantially from thosedescribed herein, will be apparent to persons skilled in the relevantart(s) based on the teachings contained herein. Such alternateembodiments fall within the scope and spirit of the present invention.

Example implementations of the energy transfer module 6302 are disclosedin Sections 4 and 5 below.

-   -   4.3 Implementation Examples

Exemplary operational and/or structural implementations related to themethod(s), structure(s), and/or embodiments described above arepresented in Sections 4 and 5 below. These implementations are presentedfor purposes of illustration, and not limitation. The invention is notlimited to the particular implementation examples described therein.Alternate implementations (including equivalents, extensions,variations, deviations, etc., of those described herein) will beapparent to persons skilled in the relevant art(s) based on theteachings contained herein. Such alternate implementations fall withinthe scope and spirit of the present invention.

5. Implementation Examples

Exemplary operational and/or structural implementations related to themethod(s), structure(s), and/or embodiments described above arepresented in this section (and its subsections). These implementationsare presented herein for purposes of illustration, and not limitation.The invention is not limited to the particular implementation examplesdescribed herein. Alternate implementations (including equivalents,extensions, variations, deviations, etc., of those described herein)will be apparent to persons skilled in the relevant art(s) based on theteachings contained herein. Such alternate implementations fall withinthe scope and spirit of the present invention.

FIG. 63 illustrates an energy transfer system 6302, which is anexemplary embodiment of the generic aliasing system 1302 in FIG. 13. Theenergy transfer system 6302 includes an energy transfer module 6304,which receives the EM signal 1304 and an energy transfer signal 6306.The energy transfer signal 6306 includes a train of energy transferpulses having non-negligible apertures that tend away from zero time induration. The energy transfer pulses repeat at an aliasing rate F_(AR).

The energy transfer module 6304 transfers energy from the EM signal 1304at the aliasing rate of the energy transfer signal 6306, as described inthe sections above with respect to the flowcharts 4601 in FIG. 46A, 4607in FIG. 46B, 4613 in FIGS. 46C and 4619 in FIG. 46D. The energy transfermodule 6304 outputs a down-converted signal 1308B, which includesnon-negligible amounts of energy transferred from the EM signal 1304.

FIG. 64A illustrates an exemplary gated transfer system 6402, which isan example of the energy transfer system 6302. The gated transfer system6402 includes a gated transfer module 6404, which is described below.

FIG. 64B illustrates an exemplary inverted gated transfer system 6406,which is an alternative example of the energy transfer system 6302. Theinverted gated transfer system 6406 includes an inverted gated transfermodule 6408, which is described below.

-   -   5.1 The Energy Transfer System as a Gated Transfer System

FIG. 64A illustrates the exemplary gated transfer system 6402, which isan exemplary implementation of the energy transfer system 6302. Thegated transfer system 6402 includes the gated transfer module 6404,which receives the EM signal 1304 and the energy transfer signal 6306.The energy transfer signal 6306 includes a train of energy transferpulses having non-negligible apertures that tend away from zero time induration. The energy transfer pulses repeat at an aliasing rate F_(AR).

The gated transfer module 6404 transfers energy from the EM signal 1304at the aliasing rate of the energy transfer signal 6306, as described inthe sections above with respect to the flowcharts 4601 in FIG. 46A, 4607in FIG. 46B, 4613 in FIGS. 46C and 4619 in FIG. 46D. The gated transfermodule 6404 outputs the down-converted signal 1308B, which includesnon-negligible amounts of energy transferred from the EM signal 1304.

-   -   -   5.1.1 The Gated Transfer System as a Switch Module and a            Storage Module

FIG. 65 illustrates an example embodiment of the gated transfer module6404 as including a switch module 6502 and a storage module 6506.Preferably, the switch module 6502 and the storage module 6506 transferenergy from the EM signal 1304 to down-convert it in any of the mannersshown in the operational flowcharts 4601 in FIG. 46A, 4607 in FIG. 46B,4613 in FIGS. 46C and 4619 in FIG. 46D.

For example, operation of the switch module 6502 and the storage module6506 is now described for down-converting the EM signal 1304 to anintermediate signal, with reference to the flowchart 4607 and theexample timing diagrams in FIG. 83A–F.

In step 4608, the switch module 6502 receives the EM signal 1304 (FIG.83A). In step 4610, the switch module 6502 receives the energy transfersignal 6306 (FIG. 83C). In step 4612, the switch module 6502 and thestorage module 6506 cooperate to transfer energy from the EM signal 1304and down-convert it to an intermediate signal. More specifically, duringstep 4612, the switch module 6502 closes during each energy transferpulse to couple the EM signal 1304 to the storage module 6506. In anembodiment, the switch module 6502 closes on rising edges of the energytransfer pulses. In an alternative embodiment, the switch module 6502closes on falling edges of the energy transfer pulses. While the EMsignal 1304 is coupled to the storage module 6506, non-negligibleamounts of energy are transferred from the EM signal 1304 to the storagemodule 6506. FIG. 83B illustrates the EM signal 1304 after the energy istransferred from it. FIG. 83D illustrates the transferred energy storedin the storage module 6506. The storage module 6506 outputs thetransferred energy as the down-converted signal 1308B. The storagemodule 6506 can output the down-converted signal 1308B as an unfilteredsignal such as signal shown in FIG. 83E, or as a filtered down-convertedsignal (FIG. 83F).

-   -   -   5.1.2 The Gated Transfer System as Break-Before-Make Module

FIG. 67A illustrates an example embodiment of the gated transfer module6404 as including a break-before-make module 6702 and a storage module6716. Preferably, the break before make module 6702 and the storagemodule 6716 transfer energy from the EM signal 1304 to down-convert itin any of the manners shown in the operational flowcharts 4601 in FIG.46A, 4607 in FIG. 46B, 4613 in FIGS. 46C and 4619 in FIG. 46D.

In FIG. 67A, the break-before-make module 6702 includes a includes anormally open switch 6704 and a normally closed switch 6706. Thenormally open switch 6704 is controlled by the energy transfer signal6306. The normally closed switch 6706 is controlled by an isolationsignal 6712. In an embodiment, the isolation signal 6712 is generatedfrom the energy transfer signal 6306. Alternatively, the energy transfersignal 6306 is generated from the isolation signal 6712. Alternatively,the isolation signal 6712 is generated independently from the energytransfer signal 6306. The break-before-make module 6702 substantiallyisolates an input 6708 from an output 6710.

FIG. 67B illustrates an example timing diagram of the energy transfersignal 6306, which controls the normally open switch 6704. FIG. 67Cillustrates an example timing diagram of the isolation signal 6712,which controls the normally closed switch 6706. Operation of thebreak-before-make module 6702 is now described with reference to theexample timing diagrams in FIGS. 67B and 67C.

Prior to time t0, the normally open switch 6704 and the normally closedswitch 6706 are at their normal states.

At time t0, the isolation signal 6712 in FIG. 67C opens the normallyclosed switch 6706. Thus, just after time t0, the normally open switch6704 and the normally closed switch 6706 are open and the input 6708 isisolated from the output 6710.

At time t1, the energy transfer signal 6306 in FIG. 67B closes thenormally open switch 6704 for the non-negligible duration of a pulse.This couples the EM signal 1304 to the storage module 6716.

Prior to t2, the energy transfer signal 6306 in FIG. 67B opens thenormally open switch 6704. This de-couples the EM signal 1304 from thestorage module 6716.

At time t2, the isolation signal 6712 in FIG. 67C closes the normallyclosed switch 6706. This couples the storage module 6716 to the output6710.

The storage module 6716, is similar to the storage module 6506 FIG. 65.The break-before-make gated transfer system 6701 down-converts the EMsignal 1304 in a manner similar to that described with reference to thegated transfer system 6501 in FIG. 65.

-   -   -   5.1.3 Example Implementations of the Switch Module

The switch module 6502 in FIG. 65 and the switch modules 6704 and 6706in FIG. 67A can be any type of switch device that preferably has arelatively low impedance when closed and a relatively high impedancewhen open. The switch modules 6502, 6704 and 6706 can be implementedwith normally open or normally closed switches. The switch modules neednot be ideal switch modules.

FIG. 66B illustrates the switch modules 6502, 6704 and 6706 as a switchmodule 6610. Switch module 6610 can be implemented in either normallyopen or normally closed architecture. The switch module 6610 (e.g.,switch modules 6502, 6704 and 6706) can be implemented with any type ofsuitable switch device, including, but not limited, to mechanical switchdevices and electrical switch devices, optical switch devices, etc., andcombinations thereof. Such devices include, but are not limited totransistor switch devices, diode switch devices, relay switch devices,optical switch devices, micro-machine switch devices, etc., orcombinations thereof.

In an embodiment, the switch module 6610 can be implemented as atransistor, such as, for example, a field effect transistor (FET), abi-polar transistor, or any other suitable circuit switching device.

In FIG. 66A, the switch module 6610 is illustrated as a FET 6602. TheFET 6602 can be any type of FET, including, but not limited to, aMOSFET, a JFET, a GaAsFET, etc. The FET 6602 includes a gate 6604, asource 6606 and a drain 6608. The gate 6604 receives the energy transfersignal 6306 to control the switching action between the source 6606 andthe drain 6608. In an embodiment, the source 6606 and the drain 6608 areinterchangeable.

It should be understood that the illustration of the switch module 6610as a FET 6602 in FIG. 66A is for example purposes only. Any devicehaving switching capabilities could be used to implement the switchmodule 6610 (i.e., switch modules 6502, 6704 and 6706), as will beapparent to persons skilled in the relevant art(s) based on thediscussion contained herein.

In FIG. 66C, the switch module 6610 is illustrated as a diode switch6612, which operates as a two lead device when the energy transfersignal 6306 is coupled to the output 6613.

In FIG. 66D, the switch module 6610 is illustrated as a diode switch6614, which operates as a two lead device when the energy transfersignal 6306 is coupled to the output 6615.

-   -   -   5.1.4 Example Implementations of the Storage Module

The storage modules 6506 and 6716 store non-negligible amounts of energyfrom the EM signal 1304. In an exemplary embodiment, the storage modules6506 and 6716 are implemented as a reactive storage module 6801 in FIG.68A, although the invention is not limited to this embodiment. Areactive storage module is a storage module that employs one or morereactive electrical components to store energy transferred from the EMsignal 1304. Reactive electrical components include, but are not limitedto, capacitors and inductors.

In an embodiment, the storage modules 6506 and 6716 include one or morecapacitive storage elements, illustrated in FIG. 68B as a capacitivestorage module 6802. In FIG. 68C, the capacitive storage module 6802 isillustrated as one or more capacitors illustrated generally ascapacitor(s) 6804.

The goal of the storage modules 6506 and 6716 is to store non-negligibleamounts of energy transferred from the EM signal 1304. Amplitudereproduction of the original, unaffected EM input signal is notnecessarily important. In an energy transfer environment, the storagemodule preferably has the capacity to handle the power beingtransferred, and to allow it to accept a non-negligible amount of powerduring a non-negligible aperture period.

A terminal 6806 serves as an output of the capacitive storage module6802. The capacitive storage module 6802 provides the stored energy atthe terminal 6806. FIG. 68F illustrates the capacitive storage module6802 as including a series capacitor 6812, which can be utilized in aninverted gated transfer system described below.

In an alternative embodiment, the storage modules 6506 and 6716 includeone or more inductive storage elements, illustrated in FIG. 68D as aninductive storage module 6808.

In an alternative embodiment, the storage modules 6506 and 6716 includea combination of one or more capacitive storage elements and one or moreinductive storage elements, illustrated in FIG. 68E as acapacitive/inductive storage module 6810.

FIG. 68G illustrates an integrated gated transfer system 6818 that canbe implemented to down-convert the EM signal 1304 as illustrated in, anddescribed with reference to, FIGS. 83A–F.

-   -   -   5.1.5 Optional Energy Transfer Signal Module

FIG. 69 illustrates an energy transfer system 6901, which is an exampleembodiment of the energy transfer system 6302. The energy transfersystem 6901 includes an optional energy transfer signal module 6902,which can perform any of a variety of functions or combinations offunctions including, but not limited to, generating the energy transfersignal 6306.

In an embodiment, the optional energy transfer signal module 6902includes an aperture generator, an example of which is illustrated inFIG. 68J as an aperture generator 6820. The aperture generator 6820generates non-negligible aperture pulses 6826 from an input signal 6824.The input signal 6824 can be any type of periodic signal, including, butnot limited to, a sinusoid, a square wave, a saw-tooth wave, etc.Systems for generating the input signal 6824 are described below.

The width or aperture of the pulses 6826 is determined by delay throughthe branch 6822 of the aperture generator 6820. Generally, as thedesired pulse width increases, the difficulty in meeting therequirements of the aperture generator 6820 decrease. In other words, togenerate non-negligible aperture pulses for a given EM input frequency,the components utilized in the example aperture generator 6820 do notrequire as fast reaction times as those that are required in anunder-sampling system operating with the same EM input frequency.

The example logic and implementation shown in the aperture generator6820 are provided for illustrative purposes only, and are not limiting.The actual logic employed can take many forms. The example aperturegenerator 6820 includes an optional inverter 6828, which is shown forpolarity consistency with other examples provided herein.

An example implementation of the aperture generator 6820 is illustratedin FIG. 68K. Additional examples of aperture generation logic areprovided in FIGS. 68H and 68I. FIG. 68H illustrates a rising edge pulsegenerator 6840, which generates pulses 6826 on rising edges of the inputsignal 6824. FIG. 68I illustrates a falling edge pulse generator 6850,which generates pulses 6826 on falling edges of the input signal 6824.

In an embodiment, the input signal 6824 is generated externally of theenergy transfer signal module 6902, as illustrated in FIG. 69.Alternatively, the input signal 6924 is generated internally by theenergy transfer signal module 6902. The input signal 6824 can begenerated by an oscillator, as illustrated in FIG. 68L by an oscillator6830. The oscillator 6830 can be internal to the energy transfer signalmodule 6902 or external to the energy transfer signal module 6902. Theoscillator 6830 can be external to the energy transfer system 6901. Theoutput of the oscillator 6830 may be any periodic waveform.

The type of down-conversion performed by the energy transfer system 6901depends upon the aliasing rate of the energy transfer signal 6306, whichis determined by the frequency of the pulses 6826. The frequency of thepulses 6826 is determined by the frequency of the input signal 6824. Forexample, when the frequency of the input signal 6824 is substantiallyequal to a harmonic or a sub-harmonic of the EM signal 1304, the EMsignal 1304 is directly down-converted to baseband (e.g. when the EMsignal is an AM signal or a PM signal), or converted from FM to a non-FMsignal. When the frequency of the input signal 6824 is substantiallyequal to a harmonic or a sub-harmonic of a difference frequency, the EMsignal 1304 is down-converted to an intermediate signal.

The optional energy transfer signal module 6902 can be implemented inhardware, software, firmware, or any combination thereof.

-   -   5.2 The Energy Transfer System as an Inverted Gated Transfer        System

FIG. 64B illustrates an exemplary inverted gated transfer system 6406,which is an exemplary implementation of the energy transfer system 6302.The inverted gated transfer system 6406 includes an inverted gatedtransfer module 6408, which receives the EM signal 1304 and the energytransfer signal 6306. The energy transfer signal 6306 includes a trainof energy transfer pulses having non-negligible apertures that tend awayfrom zero time in duration. The energy transfer pulses repeat at analiasing rate F_(AR). The inverted gated transfer module 6408 transfersenergy from the EM signal 1304 at the aliasing rate of the energytransfer signal 6306, as described in the sections above with respect tothe flowcharts 4601 in FIG. 46A, 4607 in FIG. 46B, 4613 in FIGS. 46C and4619 in FIG. 46D. The inverted gated transfer module 6408 outputs thedown-converted signal 1308B, which includes non-negligible amounts ofenergy transferred from the EM signal 1304.

-   -   -   5.2.1 The Inverted Gated Transfer System as a Switch Module            and a Storage Module

FIG. 74 illustrates an example embodiment of the inverted gated transfermodule 6408 as including a switch module 7404 and a storage module 7406.Preferably, the switch module 7404 and the storage module 7406 transferenergy from the EM signal 1304 to down-convert it in any of the mannersshown in the operational flowcharts 4601 in FIG. 46A, 4607 in FIG. 46B,4613 in FIGS. 46C and 4619 in FIG. 46D.

The switch module 7404 can be implemented as described above withreference to FIGS. 66A–D. The storage module 7406 can be implemented asdescribed above with reference to FIGS. 68A–F.

In the illustrated embodiment, the storage module 7206 includes one ormore capacitors 7408. The capacitor(s) 7408 are selected to pass higherfrequency components of the EM signal 1304 through to a terminal 7410,regardless of the state of the switch module 7404. The capacitor 7408stores non-negligible amounts of energy from the EM signal 1304.Thereafter, the signal at the terminal 7410 is off-set by an amountrelated to the energy stored in the capacitor 7408.

Operation of the inverted gated transfer system 7401 is illustrated inFIGS. 75A–F. FIG. 75A illustrates the EM signal 1304. FIG. 75Billustrates the EM signal 1304 after transferring energy from it. FIG.75C illustrates the energy transfer signal 6306, which includes a trainof energy transfer pulses having non-negligible apertures.

FIG. 75D illustrates an example down-converted signal 1308B. FIG. 75Eillustrates the down-converted signal 1308B on a compressed time scale.Since the storage module 7406 is a series element, the higherfrequencies (e.g., RF) of the EM signal 1304 can be seen on thedown-converted signal. This can be filtered as illustrated in FIG. 75F.

The inverted gated transfer system 7401 can be used to down-convert anytype of EM signal, including modulated carrier signals and unmodulatedcarrier signals.

-   -   5.3 Rail to Rail Operation for Improved Dynamic Range        -   5.3.1 Introduction

FIG. 110A illustrates aliasing module 11000 that down-converts EM signal11002 to down-converted signal 11012 using aliasing signal 11014(sometimes called an energy transfer signal). Aliasing module 11000 isan example of energy transfer module 6304 in FIG. 63. Aliasing module11000 includes UFT module 11004 and storage module 11008. As shown inFIG. 110A, UFT module 11004 is implemented as a n-channel FET 11006, andstorage module 11008 is implemented as a capacitor 11010, although theinvention is not limited to this embodiment.

FET 11006 receives the EM signal 11002 and aliasing signal 11014. In oneembodiment, aliasing signal 11014 includes a train of pulses havingnon-negligible apertures that repeat at an aliasing rate. The aliasingrate may be harmonic or sub-harmonic of the EM signal 11002. FET 11006samples EM signal 11002 at the aliasing rate of aliasing signal 11014 togenerate down-converted signal 11012. In one embodiment, aliasing signal11014 controls the gate of FET 11006 so that FET 11006 conducts (orturns on) when the FET gate-to-source voltage (V_(GS)) exceeds athreshold voltage (V_(T)). When the FET 11006 conducts, a channel iscreated from source to drain of FET 11006 so that charge is transferredfrom the EM signal 11002 to the capacitor 11010. More specifically, theFET 11006 conductance (1/R) vs V_(GS) is a continuous function thatreaches an acceptable level at V_(T), as illustrated in FIG. 110B. Thecharge stored by capacitor 11010 during successive samples formsdown-converted signal 11012.

As stated above, n-channel FET 11006 conducts when V_(GS) exceeds thethreshold voltage V_(T). As shown in FIG. 110A, the gate voltage of FET11006 is determined by aliasing signal 11014, and the source voltage isdetermined by the input EM signal 11002. Aliasing signal 11014 ispreferably a plurality of pulses whose amplitude is predictable and setby a system designer. However, the EM signal 11002 is typically receivedover a communications medium by a coupling device (such as antenna).Therefore, the amplitude of EM signal 11102 may be variable anddependent on a number of factors including the strength of thetransmitted signal, and the attenuation of the communications medium.Thus, the source voltage on FET 11006 is not entirely predictable andwill affect V_(GS) and the conductance of FET 11006, accordingly.

For example, FIG. 111A illustrates EM signal 11102, which is an exampleof EM signal 11002 that appears on the source of FET 11006. EM signal11102 has a section 11104 with a relatively high amplitude as shown.FIG. 111B illustrates the aliasing signal 11106 as an example ofaliasing signal 11014 that controls the gate of FET 11006. FIG. 111Cillustrates V_(GS) 11108, which is the difference between the gate andsource voltages shown in FIGS. 111B and 111A, respectively. FET 11006has an inherent threshold voltage V_(T) 11112 shown in FIG. 111C, abovewhich FET 11006 conducts. It is preferred that V_(GS)>V_(T) during eachpulse of aliasing signal 11106, so that FET 11006 conducts and charge istransferred from the EM signal 11102 to the capacitor 11010 during eachpulse of aliasing signal 11106. As shown in FIG. 111C, the highamplitude section 11104 of EM signal 11102 causes a V_(GS) pulse 11110that does exceed the V_(T) 11112, and therefore FET 11006 will not fullyconduct as is desired. Therefore, the resulting sample of EM signal11102 may be degraded, which potentially negatively affects thedown-converted signal 11012.

As stated earlier, the conductance of FET 11006 vs V_(GS) ismathematically continuous and is not a hard cutoff. In other words, FET11006 will marginally conduct when controlled by pulse 11110, eventhough pulse 11110 is below V_(T) 11112. However, the insertion loss ofFET 11006 will be increased when compared with a V_(GS) pulse 11111,which is greater than V_(T) 11112. The performance reduction caused by alarge amplitude input signal is often referred to as clipping orcompression. Clipping causes distortion in the down-converted signal11012, which adversely affects the faithful down-conversion of input EMsignal 11102. Dynamic range is a figure of merit associated with therange of input signals that can be faithfully down-converted withoutintroducing distortion in the down-converted signal. The higher thedynamic range of a down-conversion circuit, the larger the input signalsthat can down-converted without introducing distortion in thedown-converted signal.

-   -   -   5.3.2 Complementary UFT Structure for Improved Dynamic Range

FIG. 112 illustrates aliasing module 11200, according to an embodimentof the invention, that down-converts EM signal 11208 to generatedown-converted signal 11214 using aliasing signal 11220. Aliasing module11200 is able to down-convert input signals over a larger amplituderange as compared to aliasing module 11000, and therefore aliasingmodule 11200 has an improved dynamic range when compared with aliasingmodule 11000. The dynamic range improvement occurs because aliasingmodule 11200 includes two UFT modules that are implemented withcomplementary FET devices. In other words, one FET is n-channel, and theother FET is p-channel, so that at least one FET is always conductingduring an aliasing signal pulse, assuming the input signal does notexceed the power supply constraints. Aliasing module 11200 includes:delay 11202; UFT modules 11206, 11216; nodes 11210, 11212; and inverter11222. Inverter 11222 is tied to voltage supplies V₊ 11232 and V⁻ 11234.UFT module 11206 comprises n-channel FET 11204, and UFT module 11216comprises p-channel FET 11218.

As stated, aliasing module 11200 operates two complementary FETs toextend the dynamic range and reduce any distortion effects. Thisrequires that two complementary aliasing signals 11224, 11226 begenerated from aliasing signal 11220 to control the sampling by FETs11218, 11204, respectively. To do so, inverter 11222 receives andinverts aliasing signal 11220 to generate aliasing signal 11224 thatcontrols p-channel FET 11218. Delay 11202 delays aliasing signal 11220to generate aliasing signal 11226, where the amount of time delay isapproximately equivalent to that associated with inverter 11222. Assuch, aliasing signals 11224 and 11226 are approximately complementaryin amplitude.

Node 11210 receives EM signal 11208, and couples EM signals 11227, 11228to the sources of n-channel FET 11204 and p-channel FET 11218,respectively, where EM signals 11227, 11228 are substantially replicasof EM signal 11208. N-channel FET 11204 samples EM signal 11227 ascontrolled by aliasing signal 11226, and produces samples 11236 at thedrain of FET 11204. Likewise, p-channel FET 11218 samples EM signal11228 as controlled by aliasing signal 11224, and produces samples 11238at the drain of FET 11218. Node 11212 combines the resulting chargesamples into charge samples 11240, which are stored by capacitor 11230.The charge stored by capacitor 11230 during successive samples formsdown-converted signal 11214. Aliasing module 11200 offers improveddynamic range over aliasing module 11000 because n-channel FET 11204 andp-channel FET 11214 are complementary devices. Therefore, if one deviceis cutoff because of a large input EM signal 11208, the other devicewill conduct and sample the input signal, as long as the input signal isbetween the power supply voltages V₊ 11232 and V⁻ 11234. This is oftenreferred to as rail-to-rail operation as will be understood by thoseskilled in the arts.

For example, FIG. 113A illustrates EM signal 11302 which is an exampleof EM signals 11227, 11228 that are coupled to the sources of n-channelFET 11204 and p-channel FET 11218, respectively. As shown, EM signal11302 has a section 11304 with a relatively high amplitude includingpulses 11303, 11305. FIG. 113B illustrates the aliasing signal 11306 asan example of aliasing signal 11226 that controls the gate of n-channelFET 11204. Likewise for the p-channel FET, FIG. 113D illustrates thealiasing signal 11314 as an example of aliasing signal 11224 thatcontrols the gate of p-channel FET 11218. Aliasing signal 11314 is theamplitude complement of aliasing signal 11306.

FIG. 113C illustrates V_(GS) 11308, which is the difference between thegate and source voltages on n-channel FET 11204 that are depicted inFIGS. 113B and 113A, respectively. FIG. 113C also illustrates theinherent threshold voltage V_(T) 11309 for FET 11204, above which FET11204 conducts. Likewise for the p-channel FET, FIG. 113E illustratesV_(GS) 11316, which is the difference between the gate and sourcevoltages for p-channel FET 11218 that are depicted in FIGS. 113D and113A, respectively. FIG. 113E also illustrates the inherent thresholdvoltage V_(T) 11317 for FET 11218, below which FET 11218 conducts.

As stated, n-channel FET 11204 conducts when V_(GS) 11308 exceeds VT11309, and p-channel FET 11218 conducts when V_(GS) 11316 drops below VT11317. As illustrated by FIG. 113C, n-channel FET 11204 conducts overthe range of EM signal 11302 depicted in FIG. 113A, except for the EMsignal pulse 11305 that results in a corresponding V_(GS) pulse 11310(FIG. 113C) that does not exceed V_(T) 11309. However, p-channel FET11218 does conduct because the same EM signal pulse 11305 causes aV_(GS) pulse 11320 (FIG. 113E) that drops well below that of V_(T) 11317for the p-channel FET. Therefore, the sample of the EM signal 11302 isproperly taken by p-channel FET 11218, and no distortion is introducedin down-converted signal 11214. Similarly, EM signal pulse 11303 resultsin V_(GS) pulse 11322 (FIG. 113E) that is inadequate for the p-channelFET 11218 to fully conduct. However, n-channel FET 11204 does fullyconduct because the same EM signal pulse 11303 results in a V_(GS) 11311(FIG. 113C) that greatly exceeds V_(T) 11309.

As illustrated above, aliasing module 11200 offers an improvement indynamic range over aliasing module 11000 because of the complimentaryFET structure. Any input signal that is within the power supply voltagesV₊ 11232 and V⁻ 11234 will cause either FET 11204 or FET 11218 toconduct, or cause both FETs to conduct, as is demonstrated by FIGS.113A–113E. This occurs because any input signal that produces a V_(GS)that cuts-off the n-channel FET 11204 will push the p-channel FET 11218into conduction. Likewise, any input signal that cuts-off the p-channelFET 11218 will push the n-channel FET 11204 into conduction, andtherefore prevent any distortion of the down-converted output signal.

-   -   -   5.3.3 Biased Configurations

FIG. 114 illustrates aliasing module 11400, which is an alternateembodiment of aliasing module 11200. Aliasing module 11400 includespositive voltage supply (V₊) 11402, resistors 11404, 11406, and theelements in aliasing module 11200. V₊ 11402 and resistors 11404, 11406produce a positive DC voltage at node 11405. This allows node 11405 todrive a coupled circuit that requires a positive voltage supply, andenables unipolar supply operation of aliasing module 11400. The positivesupply voltage also has the effect of raising the DC level of the inputEM signal 11208. As such, any input signal that is within the powersupply voltages V₊ 11402 and ground will cause either FET 11204 or FET11218 to conduct, or cause both FETs to conduct, as will be understoodby those skilled in the arts based on the discussion herein.

FIG. 115 illustrates aliasing module 11500, which is an alternate biasedconfiguration of aliasing module 11200. Aliasing module 11500 includespositive voltage supply 11502, negative voltage supply 11508, resistors11504, 11506, and the elements in aliasing module 11200. The use of botha positive and negative voltage supply allows for node 11505 to bebiased anywhere between V₊ 11502 and V⁻ 11508. This allows node 11505 todrive a coupled circuit that requires either a positive or negativesupply voltage. Furthermore, any input signal that is within the powersupply voltages V⁺ 11502 and V⁻ 11508 will cause either FET 11204 or FET11218 to conduct, or cause both FETs to conduct, as will be understoodby those skilled in the arts based on the discussion herein.

-   -   -   5.3.4 Simulation Examples

As stated, an aliasing module with a complementary FET structure offersimproved dynamic range when compared with a single (or unipolar) FETconfiguration. This is further illustrated by comparing the signalwaveforms associated aliasing module 11602 (of FIG. 116) which has acomplementary FET structure, with that of aliasing module 11702 (of FIG.117) which has a single (or unipolar) FET structure.

Aliasing module 11602 (FIG. 116) down-converts EM signal 11608 usingaliasing signal 11612 to generate down-converted signal 11610. Aliasingmodule 11602 has a complementary FET structure and includes n-channelFET 11604, p-channel FET 11606, inverter 11614, and aliasing signalgenerator 11608. Aliasing module 11602 is biased by supply circuit 11616as is shown. Aliasing module 11702 (FIG. 117) down-converts EM signal11704 using aliasing signal 11708 to generate down-converted signal11706. Aliasing module 11702 is a single FET structure comprisingn-channel FET 11712 and aliasing signal generator 11714, and is biasedusing voltage supply circuit 11710.

FIGS. 118–120 are signal waveforms that correspond to aliasing module11602, and FIGS. 121–123 are signal waveforms that correspond toaliasing module 11702. FIGS. 118 and 121 are down-converted signals11610, 11706, respectively. FIGS. 119 and 122 are the sampled EM signal11608, 11704, respectively. FIGS. 120 and 123 are the aliasing signals11612, 11708, respectively. Aliasing signal 11612 is identical toaliasing signal 11708 in order that a proper comparison between modules11602 and 11702 can be made.

EM signals 11608, 11704 are relatively large input signals that approachthe power supply voltages of ±1.65 volts, as is shown in FIGS. 119 and122, respectively. In FIG. 119, sections 11802 and 11804 of signal 11608depict energy transfer from EM signal 11608 to down-converted signal11610 during by aliasing module 11602. More specifically, section 11802depicts energy transfer near the −1.65v supply, and section 11804depicts energy transfer near the +1.65v supply. The symmetrical qualityof the energy transfer near the voltage supply rails indicates that atleast one of complementary FETs 11604, 11606 are appropriately samplingthe EM signal during each of the aliasing pulses 11612. This results ina down-converted signal 11610 that has minimal high frequency noise, andis centered between −1.0v and 1.0v (i.e. has negligible DC voltagecomponent).

Similarly in FIG. 122, sections 11902 and 11904 illustrate the energytransfer from EM signal 11704 to down-converted signal 11706 by aliasingmodule 11702 (single FET configuration). More specifically, section11902 depicts energy transfer near the −1.65v supply, and section 11904depicts energy transfer near the +1.65v supply. By comparing sections11902, 11904 with sections 11802, 11804 of FIG. 119, it is clear thatthe energy transfer in sections 11902, 11904 is not as symmetrical nearthe power supply rails as that of sections 11802, 11804. This isevidence that the EM signal 11704 is partially pinching off single FET11712 over part of the signal 11704 trace. This results in adown-converted signal 11706 that has more high frequency noise whencompared to down-converted signal 11610, and has a substantial negativeDC voltage component.

In summary, down-converted signal 11706 reflects distortion introducedby a relatively large EM signal that is pinching-off the single FET11712 in aliasing module 11702. Down-converted signal 11610 that isproduced by aliasing module 11602 is relatively distortion free. Thisoccurs because the complementary FET configuration in aliasing module11602 is able to handle input signals with large amplitudes withoutintroducing distortion in the down-converted signal 11610. Therefore,the complementary FET configuration in the aliasing module 11602 offersimproved dynamic range when compared with the single FET configurationof the aliasing module 11702.

-   -   5.4 Optimized Switch Structures        -   5.4.1 Splitter in CMOS

FIG. 124A illustrates an embodiment of a splitter circuit 12400implemented in CMOS. This embodiment is provided for illustrativepurposes, and is not limiting. In an embodiment, splitter circuit 12400is used to split a local oscillator (LO) signal into two oscillatingsignals that are approximately 90° out of phase. The first oscillatingsignal is called the I-channel oscillating signal. The secondoscillating signal is called the Q-channel oscillating signal. TheQ-channel oscillating signal lags the phase of the I-channel oscillatingsignal by approximately 90°. Splitter circuit 12400 includes a firstI-channel inverter 12402, a second I-channel inverter 12404, a thirdI-channel inverter 12406, a first Q-channel inverter 12408, a secondQ-channel inverter 12410, an I-channel flip-flop 12412, and a Q-channelflip-flop 12414.

FIGS. 124F–J are example waveforms used to illustrate signalrelationships of splitter circuit 12400. The waveforms shown in FIGS.124F–J reflect ideal delay times through splitter circuit 12400components. LO signal 12416 is shown in FIG. 124F. First, second, andthird I-channel inverters 12402, 12404, and 12406 invert LO signal 12416three times, outputting inverted LO signal 12418, as shown in FIG. 124G.First and second Q-channel inverters 12408 and 12410 invert LO signal12416 twice, outputting non-inverted LO signal 12420, as shown in FIG.124H. The delay through first, second, and third I-channel inverters12402, 12404, and 12406 is substantially equal to that through first andsecond Q-channel inverters 12408 and 12410, so that inverted LO signal12418 and non-inverted LO signal 12420 are approximately 180° out ofphase. The operating characteristics of the inverters may be tailored toachieve the proper delay amounts, as would be understood by personsskilled in the relevant art(s).

I-channel flip-flop 12412 inputs inverted LO signal 12418. Q-channelflip-flop 12414 inputs non-inverted LO signal 12420. In the currentembodiment, I-channel flip-flop 12412 and Q-channel flip-flop 12414 areedge-triggered flip-flops. When either flip-flop receives a rising edgeon its input, the flip-flop output changes state. Hence, I-channelflip-flop 12412 and Q-channel flip-flop 12414 each output signals thatare approximately half of the input signal frequency. Additionally, aswould be recognized by persons skilled in the relevant art(s), becausethe inputs to I-channel flip-flop 12412 and Q-channel flip-flop 12414are approximately 180° out of phase, their resulting outputs are signalsthat are approximately 90° out of phase. I-channel flip-flop 12412outputs I-channel oscillating signal 12422, as shown in FIG. 124I.Q-channel flip-flop 12414 outputs Q-channel oscillating signal 12424, asshown in FIG. 124J. Q-channel oscillating signal 12424 lags the phase ofI-channel oscillating signal 12422 by 90°, also as shown in a comparisonof FIGS. 124I and 124J.

FIG. 124B illustrates a more detailed circuit embodiment of the splittercircuit 12400 of FIG. 124. The circuit blocks of FIG. 124B that aresimilar to those of FIG. 124A are indicated by corresponding referencenumbers. FIGS. 124C–D show example output waveforms relating to thesplitter circuit 12400 of FIG. 124B. FIG. 124C shows I-channeloscillating signal 12422. FIG. 124D shows Q-channel oscillating signal12424. As is indicated by a comparison of FIGS. 124C and 124D, thewaveform of Q-channel oscillating signal 12424 of FIG. 124D lags thewaveform of I-channel oscillating signal 12422 of FIG. 124C byapproximately 90°.

It should be understood that the illustration of the splitter circuit12400 in FIGS. 124A and 124B is for example purposes only. Splittercircuit 12400 may be comprised of an assortment of logic andsemiconductor devices of a variety of types, as will be apparent topersons skilled in the relevant art(s) based on the discussion containedherein.

-   -   -   5.4.2 I/Q Circuit

FIG. 124E illustrates an example embodiment of a complete I/Q circuit12426 in CMOS. I/Q circuit 12426 includes a splitter circuit 12400 asdescribed in detail above. Further description regarding I/Q circuitimplementations are provided herein, including the applicationsreferenced above.

-   -   5.5 Example I and Q Implementations        -   5.5.1 Switches of Different Sizes

In an embodiment, the switch modules discussed herein can be implementedas a series of switches operating in parallel as a single switch. Theseries of switches can be transistors, such as, for example, fieldeffect transistors (FET), bi-polar transistors, or any other suitablecircuit switching devices. The series of switches can be comprised ofone type of switching device, or a combination of different switchingdevices.

For example, FIG. 125 illustrates a switch module 12500. In FIG. 125,the switch module is illustrated as a series of FETs 12502 a–n. The FETs12502 a–n can be any type of FET, including, but not limited to, aMOSFET, a JFET, a GaAsFET, etc. Each of FETs 12502 a–n includes a gate12504 a–n, a source 12506 a–n, and a drain 12508 a–n, similarly to thatof FET 2802 of FIG. 28A. The series of FETs 12502 a–n operate inparallel. Gates 12504 a–n are coupled together, sources 12506 a–n arecoupled together, and drains 12508 a–n are coupled together. Each ofgates 12504 a–n receives the control signal 1604, 8210 to control theswitching action between corresponding sources 12506 a–n and drains12508 a–n. Generally, the corresponding sources 12506 a–n and drains12508 a–n of each of FETs 12502 a–n are interchangeable. There is nonumerical limit to the number of FETs. Any limitation would depend onthe particular application, and the “a–n” designation is not meant tosuggest a limit in any way.

In an embodiment, FETs 12502 a–n have similar characteristics. Inanother embodiment, one or more of FETs 12502 a–n have differentcharacteristics than the other FETs. For example, FETs 12502 a–n may beof different sizes. In CMOS, generally, the larger size a switch is(meaning the larger the area under the gate between the source and drainregions), the longer it takes for the switch to turn on. The longer turnon time is due in part to a higher gate to channel capacitance thatexists in larger switches. Smaller CMOS switches turn on in less time,but have a higher channel resistance. Larger CMOS switches have lowerchannel resistance relative to smaller CMOS switches. Different turn oncharacteristics for different size switches provides flexibility indesigning an overall switch module structure. By combining smallerswitches with larger switches, the channel conductance of the overallswitch structure can be tailored to satisfy given requirements.

In an embodiment, FETs 12502 a–n are CMOS switches of different relativesizes. For example, FET 12502 a may be a switch with a smaller sizerelative to FETs 12502 b–n. FET 12502 b may be a switch with a largersize relative to FET 12502 a, but smaller size relative to FETs 12502c–n. The sizes of FETs 12502 c–n also may be varied relative to eachother. For instance, progressively larger switch sizes may be used. Byvarying the sizes of FETs 12502 a–n relative to each other, the turn oncharacteristic curve of the switch module can be correspondingly varied.For instance, the turn on characteristic of the switch module can betailored such that it more closely approaches that of an ideal switch.Alternately, the switch module could be tailored to produce a shapedconductive curve.

By configuring FETs 12502 a–n such that one or more of them are of arelatively smaller size, their faster turn on characteristic can improvethe overall switch module turn on characteristic curve. Because smallerswitches have a lower gate to channel capacitance, they can turn on morerapidly than larger switches.

By configuring FETs 12502 a–n such that one or more of them are of arelatively larger size, their lower channel resistance also can improvethe overall switch module turn on characteristics. Because largerswitches have a lower channel resistance, they can provide the overallswitch structure with a lower channel resistance, even when combinedwith smaller switches. This improves the overall switch structure'sability to drive a wider range of loads. Accordingly, the ability totailor switch sizes relative to each other in the overall switchstructure allows for overall switch structure operation to more nearlyapproach ideal, or to achieve application specific requirements, or tobalance trade-offs to achieve specific goals, as will be understood bypersons skilled in the relevant arts(s) from the teachings herein.

It should be understood that the illustration of the switch module as aseries of FETs 12502 a–n in FIG. 125 is for example purposes only. Anydevice having switching capabilities could be used to implement theswitch module (e.g., switch modules 2802, 2702, 2404 and 2406), as willbe apparent to persons skilled in the relevant art(s) based on thediscussion contained herein.

-   -   -   5.5.2 Reducing Overall Switch Area

Circuit performance also can be improved by reducing overall switcharea. As discussed above, smaller switches (i.e., smaller area under thegate between the source and drain regions) have a lower gate to channelcapacitance relative to larger switches. The lower gate to channelcapacitance allows for lower circuit sensitivity to noise spikes. FIG.126A illustrates an embodiment of a switch module, with a large overallswitch area. The switch module of FIG. 126A includes twenty FETs12602–12640. As shown, FETs 12602–12640 are the same size (“Wd” and“lng” parameters are equal). Input source 12646 produces the input EMsignal. Pulse generator 12648 produces the energy transfer signal forFETs 12602–12640. Capacitor C1 is the storage element for the inputsignal being sampled by FETs 12602–12640. FIGS. 126B–126Q illustrateexample waveforms related to the switch module of FIG. 126A. FIG. 126Bshows a received 1.01 GHz EM signal to be sampled and downconverted to a10 MHZ intermediate frequency signal. FIG. 126C shows an energy transfersignal having an aliasing rate of 200 MHZ, which is applied to the gateof each of the twenty FETs 12602–12640. The energy transfer signalincludes a train of energy transfer pulses having non-negligibleapertures that tend away from zero time in duration. The energy transferpulses repeat at the aliasing rate. FIG. 126D illustrates the affectedreceived EM signal, showing effects of transferring energy at thealiasing rate, at point 12642 of FIG. 126A. FIG. 126E illustrates adown-converted signal at point 12644 of FIG. 126A, which is generated bythe down-conversion process.

FIG. 126F illustrates the frequency spectrum of the received 1.01 GHz EMsignal. FIG. 126G illustrates the frequency spectrum of the receivedenergy transfer signal. FIG. 126H illustrates the frequency spectrum ofthe affected received EM signal at point 12642 of FIG. 126A. FIG. 1261illustrates the frequency spectrum of the down-converted signal at point12644 of FIG. 126A.

FIGS. 126J–126M respectively further illustrate the frequency spectrumsof the received 1.01 GHz EM signal, the received energy transfer signal,the affected received EM signal at point 12642 of FIG. 126A, and thedown-converted signal at point 12644 of FIG. 126A, focusing on anarrower frequency range centered on 1.00 GHz. As shown in FIG. 126L, anoise spike exists at approximately 1.0 GHz on the affected received EMsignal at point 12642 of FIG. 126A. This noise spike may be radiated bythe circuit, causing interference at 1.0 GHz to nearby receivers.

FIGS. 126N–126Q respectively illustrate the frequency spectrums of thereceived 1.01 GHz EM signal, the received energy transfer signal, theaffected received EM signal at point 12642 of FIG. 126A, and thedown-converted signal at point 12644 of FIG. 126A, focusing on a narrowfrequency range centered near 10.0 MHZ. In particular, FIG. 126Q showsthat an approximately 5 mV signal was downconverted at approximately 10MHZ.

FIG. 127A illustrates an alternative embodiment of the switch module,this time with fourteen FETs 12702–12728 shown, rather than twenty FETs12602–12640 as shown in FIG. 126A. Additionally, the FETs are of varioussizes (some “Wd” and “lng” parameters are different between FETs).

FIGS. 127B–127Q, which are example waveforms related to the switchmodule of FIG. 127A, correspond to the similarly designated figures ofFIGS. 126B–126Q. As FIG. 127L shows, a lower level noise spike exists at1.0 GHz than at the same frequency of FIG. 126L. This correlates tolower levels of circuit radiation. Additionally, as FIG. 127Q shows, thelower level noise spike at 1.0 GHz was achieved with no loss inconversion efficiency. This is represented in FIG. 127Q by theapproximately 5 mV signal downconverted at approximately 10 MHZ. Thisvoltage is substantially equal to the level downconverted by the circuitof FIG. 126A. In effect, by decreasing the number of switches, whichdecreases overall switch area, and by reducing switch area on aswitch-by-switch basis, circuit parasitic capacitance can be reduced, aswould be understood by persons skilled in the relevant art(s) from theteachings herein. In particular this may reduce overall gate to channelcapacitance, leading to lower amplitude noise spikes and reducedunwanted circuit radiation.

It should be understood that the illustration of the switches above asFETs in FIGS. 126A–126Q and 127A–127Q is for example purposes only. Anydevice having switching capabilities could be used to implement theswitch module, as will be apparent to persons skilled in the relevantart(s) based on the discussion contained herein.

-   -   -   5.5.3 Charge Injection Cancellation

In embodiments wherein the switch modules discussed herein are comprisedof a series of switches in parallel, in some instances it may bedesirable to minimize the effects of charge injection. Minimizing chargeinjection is generally desirable in order to reduce the unwanted circuitradiation resulting therefrom. In an embodiment, unwanted chargeinjection effects can be reduced through the use of complementaryn-channel MOSFETs and p-channel MOSFETs. N-channel MOSFETs and p-channelMOSFETs both suffer from charge injection. However, because signals ofopposite polarity are applied to their respective gates to turn theswitches on and off, the resulting charge injection is of oppositepolarity. Resultingly, n-channel MOSFETs and p-channel MOSFETs may bepaired to cancel their corresponding charge injection. Hence, in anembodiment, the switch module may be comprised of n-channel MOSFETs andp-channel MOSFETS, wherein the members of each are sized to minimize theundesired effects of charge injection.

FIG. 129A illustrates an alternative embodiment of the switch module,this time with fourteen n-channel FETs 12902–12928 and twelve p-channelFETs 12930–12952 shown, rather than twenty FETs 12602–12640 as shown inFIG. 126A. The n-channel and p-channel FETs are arranged in acomplementary configuration. Additionally, the FETs are of various sizes(some “Wd” and “lng” parameters are different between FETs).

FIGS. 129B–129Q, which are example waveforms related to the switchmodule of FIG. 129A, correspond to the similarly designated figures ofFIGS. 126B–126Q. As FIG. 129L shows, a lower level noise spike exists at1.0 GHz than at the same frequency of FIG. 126L. This correlates tolower levels of circuit radiation. Additionally, as FIG. 129Q shows, thelower level noise spike at 1.0 GHz was achieved with no loss inconversion efficiency. This is represented in FIG. 129Q by theapproximately 5 mV signal downconverted at approximately 10 MHZ. Thisvoltage is substantially equal to the level downconverted by the circuitof FIG. 126A. In effect, by arranging the switches in a complementaryconfiguration, which assists in reducing charge injection, and bytailoring switch area on a switch-by-switch basis, the effects of chargeinjection can be reduced, as would be understood by persons skilled inthe relevant art(s) from the teachings herein. In particular this leadsto lower amplitude noise spikes and reduced unwanted circuit radiation.

It should be understood that the use of FETs in FIGS. 129A–129Q in theabove description is for example purposes only. From the teachingsherein, it would be apparent to persons of skill in the relevant art(s)to manage charge injection in various transistor technologies usingtransistor pairs.

-   -   -   5.5.4 Overlapped Capacitance

The processes involved in fabricating semiconductor circuits, such asMOSFETs, have limitations. In some instances, these process limitationsmay lead to circuits that do not function as ideally as desired. Forinstance, a non-ideally fabricated MOSFET may suffer from parasiticcapacitances, which in some cases may cause the surrounding circuit toradiate noise. By fabricating circuits with structure layouts as closeto ideal as possible, problems of non-ideal circuit operation can beminimized.

FIG. 128A illustrates a cross-section of an example n-channelenhancement-mode MOSFET 12800, with ideally shaped n+ regions. MOSFET12800 includes a gate 12802, a channel region 12804, a source contact12806, a source region 12808, a drain contact 12810, a drain region12812, and an insulator 12814. Source region 12808 and drain region12812 are separated by p-type material of channel region 12804. Sourceregion 12808 and drain region 12812 are shown to be n+ material. The n+material is typically implanted in the p-type material of channel region12804 by an ion implantation/diffusion process. Ionimplantation/diffusion processes are well known by persons skilled inthe relevant art(s). Insulator 12814 insulates gate 12802 which bridgesover the p-type material. Insulator 12814 generally comprises ametal-oxide insulator. The channel current between source region 12808and drain region 12812 for MOSFET 12800 is controlled by a voltage atgate 12802.

Operation of MOSFET 12800 shall now be described. When a positivevoltage is applied to gate 12802, electrons in the p-type material ofchannel region 12804 are attracted to the surface below insulator 12814,forming a connecting near-surface region of n-type material between thesource and the drain, called a channel. The larger or more positive thevoltage between the gate contact 12806 and source region 12808, thelower the resistance across the region between.

In FIG. 128A, source region 12808 and drain region 12812 are illustratedas having n+ regions that were formed into idealized rectangular regionsby the ion implantation process. FIG. 128B illustrates a cross-sectionof an example n-channel enhancement-mode MOSFET 12816 with non-ideallyshaped n+ regions. Source region 12820 and drain region 12822 areillustrated as being formed into irregularly shaped regions by the ionimplantation process. Due to uncertainties in the ionimplantation/diffusion process, in practical applications, source region12820 and drain region 12822 do not form rectangular regions as shown inFIG. 128A. FIG. 128B shows source region 12820 and drain region 12822forming exemplary irregular regions. Due to these process uncertainties,the n+ regions of source region 12820 and drain region 12822 also maydiffuse further than desired into the p-type region of channel region12818, extending underneath gate 12802. The extension of the sourceregion 12820 and drain region 12822 underneath gate 12802 is shown assource overlap 12824 and drain overlap 12826. Source overlap 12824 anddrain overlap 12826 are further illustrated in FIG. 128C. FIG. 128Cillustrates a top-level view of an example layout configuration forMOSFET 12816. Source overlap 12824 and drain overlap 12826 may lead tounwanted parasitic capacitances between source region 12820 and gate12802, and between drain region 12822 and gate 12802. These unwantedparasitic capacitances may interfere with circuit function. Forinstance, the resulting parasitic capacitances may produce noise spikesthat are radiated by the circuit, causing unwanted electromagneticinterference.

As shown in FIG. 128C, an example MOSFET 12816 may include a gate pad12828. Gate 12802 may include a gate extension 12830, and a gate padextension 12832. Gate extension 12830 is an unused portion of gate 12802required due to metal implantation process tolerance limitations. Gatepad extension 12832 is a portion of gate 12802 used to couple gate 12802to gate pad 12828. The contact required for gate pad 12828 requires gatepad extension 12832 to be of non-zero length to separate the resultingcontact from the area between source region 12820 and drain region12822. This prevents gate 12802 from shorting to the channel betweensource region 12820 and drain region 12822 (insulator 12814 of FIG. 128Bis very thin in this region). Unwanted parasitic capacitances may formbetween gate extension 12830 and the substrate (FET 12816 is fabricatedon a substrate), and between gate pad extension 12832 and the substrate.By reducing the respective areas of gate extension 12830 and gate padextension 12832, the parasitic capacitances resulting therefrom can bereduced. Accordingly, embodiments address the issues of uncertainty inthe ion implantation/diffusion process. it will be obvious to personsskilled in the relevant art(s) how to decrease the areas of gateextension 12830 and gate pad extension 12832 in order to reduce theresulting parasitic capacitances.

It should be understood that the illustration of the n-channelenhancement-mode MOSFET is for example purposes only. The presentinvention is applicable to depletion mode MOSFETs, and other transistortypes, as will be apparent to persons skilled in the relevant art(s)based on the discussion contained herein.

-   -   5.6 Other Inplementations

The implementations described above are provided for purposes ofillustration. These implementations are not intended to limit theinvention. Alternate implementations, differing slightly orsubstantially from those described herein, will be apparent to personsskilled in the relevant art(s) based on the teachings contained herein.Such alternate implementations fall within the scope and spirit of thepresent invention.

6. Optional Optimizations of Energy Transfer at an Aliasing Rate

The methods and systems described in sections above can be optimizedwith one or more of the optimization methods or systems described below.

-   -   6.1 Doubling the Aliasing Rate (F_(AR)) of the Energy Transfer        Signal

In an embodiment, the optional energy transfer signal module 6902 inFIG. 69 includes a pulse generator module that generates aliasing pulsesat twice the frequency of the oscillating source. The input signal 6828may be any suitable oscillating source.

FIG. 71 illustrates a circuit 7102 that generates a doubler outputsignal 7104 (FIG. 72B) that may be used as an energy transfer signal6306. The circuit 7102 generates pulses on both rising and falling edgesof the input oscillating signal 7106 of FIG. 72A. The circuit 7102 canbe implemented as a pulse generator and aliasing rate (F_(AR)) doubler.The doubler output signal 7104 can be used as the energy transfer signal6306.

In the example of FIG. 71, the aliasing rate is twice the frequency ofthe input oscillating signal F_(OSC) 7106, as shown by EQ. (9) below.F _(AR)=2·F _(OSC)  EQ. (9)

The aperture width of the aliasing pulses is determined by the delaythrough a first inverter 7108 of FIG. 71. As the delay is increased, theaperture is increased. A second inverter 7112 is shown to maintainpolarity consistency with examples described elsewhere. In an alternateembodiment inverter 7112 is omitted. Preferably, the pulses havenon-negligible aperture widths that tend away from zero time. Thedoubler output signal 7104 may be further conditioned as appropriate todrive the switch module with non-negligible aperture pulses. The circuit7102 may be implemented with integrated circuitry, discretely, withequivalent logic circuitry, or with any valid fabrication technology.

-   -   6.2 Differential Implementations

The invention can be implemented in a variety of differentialconfigurations. Differential configurations are useful for reducingcommon mode noise. This can be very useful in receiver systems wherecommon mode interference can be caused by intentional or unintentionalradiators such as cellular phones, CB radios, electrical appliances etc.Differential configurations are also useful in reducing any common modenoise due to charge injection of the switch in the switch module or dueto the design and layout of the system in which the invention is used.Any spurious signal that is induced in equal magnitude and equal phasein both input leads of the invention will be substantially reduced oreliminated. Some differential configurations, including some of theconfigurations below, are also useful for increasing the voltage and/orfor increasing the power of the down-converted signal 1308B.

Differential systems are most effective when used with a differentialfront end (inputs) and a differential back end (outputs). They can alsobe utilized in the following configurations, for example:

-   -   a) A single-input front end and a differential back end; and    -   b) A differential front end and a single-output back end.

Examples of these system are provided below, with a first exampleillustrating a specific method by which energy is transferred from theinput to the output differentially.

While an example of a differential energy transfer module is shownbelow, the example is shown for the purpose of illustration, notlimitation. Alternate embodiments (including equivalents, extensions,variations, deviations etc.) of the embodiment described herein will beapparent to those skilled in the relevant art based on the teachingscontained herein. The invention is intended and adapted to include suchalternate embodiments.

-   -   -   6.2.1 An Example Illustrating Energy Transfer Differentially

FIG. 76A illustrates a differential system 7602 that can be included inthe energy transfer module 6304. The differential system 7602 includesan inverted gated transfer design similar to that described withreference to FIG. 74. The differential system 7602 includes inputs 7604and 7606 and outputs 7608 and 7610. The differential system 7602includes a first inverted gated transfer module 7612, which includes astorage module 7614 and a switch module 7616. The differential system7602 also includes a second inverted gated transfer module 7618, whichincludes a storage module 7620 and a switch module 7616, which it sharesin common with inverted gated transfer module 7612.

One or both of the inputs 7604 and 7606 are coupled to an EM signalsource. For example, the inputs can be coupled to an EM signal source,wherein the input voltages at the inputs 7604 and 7606 are substantiallyequal in amplitude but 180 degrees out of phase with one another.Alternatively, where dual inputs are unavailable, one of the inputs 7604and 7606 can be coupled to ground.

In operation, when the switch module 7616 is closed, the storage modules7614 and 7620 are in series and, provided they have similar capacitivevalues, accumulate charge of equal magnitude but opposite polarities.When the switch module 7616 is open, the voltage at the output 7608 isrelative to the input 7604, and the voltage at the output 7610 isrelative to the voltage at the input 7606.

Portions of the signals at the outputs 7608 and 7610 include signalsresulting from energy stored in the storage modules 7614 and 7620,respectively, when the switch module 7616 was closed. The portions ofthe signals at the outputs 7608 and 7610 resulting from the storedcharge are generally equal in amplitude to one another but 180 degreesout of phase.

Portions of the signals at the outputs 7608 and 7610 also include ripplevoltage or noise resulting from the switching action of the switchmodule 7616. But because the switch module is positioned between the twooutputs 7608 and 7610, the noise introduced by the switch module appearsat the outputs as substantially equal and in-phase with one another. Asa result, the ripple voltage can be substantially canceled out byinverting the signal at one of the outputs 7608 or 7610 and adding it tothe other remaining output. Additionally, any noise that is impressedwith equal amplitude and equal phase onto the input terminals 7604 and7606 by any other noise sources will tend to be canceled in the sameway.

-   -   -   -   6.2.1.1 Differential Input-to-Differential Output

FIG. 76B illustrates the differential system 7602 wherein the inputs7604 and 7606 are coupled to equal and opposite EM signal sources,illustrated here as dipole antennas 7624 and 7626. In this embodiment,when one of the outputs 7608 or 7610 is inverted and added to the otheroutput, the common mode noise due to the switching module 7616 and othercommon mode noise present at the input terminals 7604 and 7606 tend tosubstantially cancel out.

-   -   -   -   6.2.1.2 Single Input-to-Differential Output

FIG. 76C illustrates the differential system 7602 wherein the input 7604is coupled to an EM signal source such as a monopole antenna 7628 andthe input 7606 is coupled to ground. In this configuration, the voltagesat the outputs 7608 and 7610 are approximately one half the value of thevoltages at the outputs in the implementation illustrated in FIG. 76B,given all other parameters are equal.

FIG. 76E illustrates an example single input to differential outputreceiver/down-converter system 7636. The system 7636 includes thedifferential system 7602 wherein the input 7606 is coupled to ground asin FIG. 76C. The input 7604 is coupled to an EM signal source 7638through an optional input impedance match 7642. The EM signal sourceimpedance can be matched with an impedance match system 7642 asdescribed in section 5 below.

The outputs 7608 and 7610 are coupled to a differential circuit 7644such as a filter, which preferably inverts one of the outputs 7608 or7610 and adds it to the other output 7608 or 7610. This substantiallycancels common mode noise generated by the switch module 7616. Thedifferential circuit 7644 preferably filters the higher frequencycomponents of the EM signal 1304 that pass through the storage modules7614 and 7620. The resultant filtered signal is output as thedown-converted signal 1308B.

-   -   -   -   6.2.1.3 Differential Input-to-Single Output

FIG. 76D illustrates the differential input to single output system 7629wherein the inputs 7604 and 7606 of the differential system 7602 arecoupled to equal and opposite EM signal dipole antennas 7630 and 7632.In system 7629, the common mode noise voltages are not canceled as insystems shown above. The output is coupled from terminal 7608 to a load7648.

-   -   -   6.2.2 Specific Alternative Embodiments

In specific alternative embodiments, the present invention isimplemented using a plurality of gated transfer modules controlled by acommon energy transfer signal with a storage module coupled between theoutputs of the plurality of gated transfer modules. For example, FIG. 99illustrates a differential system 9902 that includes first and secondgated transfer modules 9904 and 9906, and a storage module 9908 coupledbetween. Operation of the differential system 9902 will be apparent toone skilled in the relevant art(s), based on the description herein.

As with the first implementation described above in section 5.5.1 andits sub-sections, the gated transfer differential system 9902 can beimplemented with a single input, differential inputs, a single output,differential outputs, and combinations thereof. For example, FIG. 100illustrates an example single input-to-differential output system 10002.

Where common-mode rejection is desired to protect the input from variouscommon-mode effects, and where common mode rejection to protect theoutput is not necessary, a differential input-to-single outputimplementation can be utilized. FIG. 102 illustrates an exampledifferential-to-single ended system 10202, where a balance/unbalance(balun) circuit 10204 is utilized to generate the differential input.Other input configurations are contemplated. A first output 10206 iscoupled to a load 10208. A second output 10210 is coupled to groundpoint 10212.

Typically, in a balanced-to-unbalanced system, where a single output istaken from a differential system without the use of a balun, (i.e.,where one of the output signals is grounded), a loss of about 6 db isobserved. In the configuration of FIG. 102, however, the ground point10212 simply serves as a DC voltage reference for the circuit. Thesystem 10202 transfers charge from the input in the same manner as if itwere full differential, with its conversion efficiency generallyaffected only by the parasitics of the circuit components used, such asthe Rds(on) on FET switches if used in the switch module. In otherwords, the charge transfer still continues in the same manner of asingle ended implementation, providing the necessary single-ended groundto the input circuitry when the aperture is active, yet configured toallow the input to be differential for specific common-mode rejectioncapability and/or interface between a differential input and a singleended output system.

-   -   -   6.2.3 Specific Examples of Optimizations and Configurations            for Inverted and Non-Inverted Differential Designs

Gated transfer systems and inverted gated transfer systems can beimplemented with any of the various optimizations and configurationsdisclosed through the specification, such as, for example, impedancematching, tanks and resonant structures, bypass networks, etc. Forexample, the differential system 10002 in FIG. 100, which utilizes gatedtransfer modules with an input impedance matching system 10004 and atank circuit 10006, which share a common capacitor. Similarly,differential system 10102 in FIG. 101, utilizes an inverted gatedtransfer module with an input impedance matching system 10104 and a tankcircuit 10106, which share a common capacitor.

-   -   6.3 Smoothing the Down-Converted Signal

The down-converted signal 1308B may be smoothed by filtering as desired.The differential circuit 7644 implemented as a filter in FIG. 76Eillustrates but one example. This may be accomplished in any of thedescribed embodiments by hardware, firmware and software implementationas is well known by those skilled in the arts.

-   -   6.4 Impedance Matching

The energy transfer module has input and output impedances generallydefined by (1) the duty cycle of the switch module, and (2) theimpedance of the storage module, at the frequencies of interest (e.g. atthe EM input, and intermediate/baseband frequencies).

Starting with an aperture width of approximately ½ the period of the EMsignal being down-converted as a preferred embodiment, this aperturewidth (e.g. the “closed time”) can be decreased. As the aperture widthis decreased, the characteristic impedance at the input and the outputof the energy transfer module increases. Alternatively, as the aperturewidth increases from ½ the period of the EM signal being down-converted,the impedance of the energy transfer module decreases.

One of the steps in determining the characteristic input impedance ofthe energy transfer module could be to measure its value. In anembodiment, the energy transfer module's characteristic input impedanceis 300 ohms. An impedance matching circuit can be utilized toefficiently couple an input EM signal that has a source impedance of,for example, 50 ohms, with the energy transfer module's impedance of,for example, 300 ohms. Matching these impedances can be accomplished invarious manners, including providing the necessary impedance directly orthe use of an impedance match circuit as described below.

Referring to FIG. 70, a specific embodiment using an RF signal as aninput, assuming that the impedance 7012 is a relatively low impedance ofapproximately 50 Ohms, for example, and the input impedance 7016 isapproximately 300 Ohms, an initial configuration for the input impedancematch module 7006 can include an inductor 7306 and a capacitor 7308,configured as shown in FIG. 73. The configuration of the inductor 7306and the capacitor 7308 is a possible configuration when going from a lowimpedance to a high impedance. Inductor 7306 and the capacitor 7308constitute an L match, the calculation of the values which is well knownto those skilled in the relevant arts.

The output characteristic impedance can be impedance matched to takeinto consideration the desired output frequencies. One of the steps indetermining the characteristic output impedance of the energy transfermodule could be to measure its value. Balancing the very low impedanceof the storage module at the input EM frequency, the storage moduleshould have an impedance at the desired output frequencies that ispreferably greater than or equal to the load that is intended to bedriven (for example, in an embodiment, storage module impedance at adesired 1 MHz output frequency is 2K ohm and the desired load to bedriven is 50 ohms). An additional benefit of impedance matching is thatfiltering of unwanted signals can also be accomplished with the samecomponents.

In an embodiment, the energy transfer module's characteristic outputimpedance is 2K ohms. An impedance matching circuit can be utilized toefficiently couple the down-converted signal with an output impedanceof, for example, 2K ohms, to a load of, for example, 50 ohms. Matchingthese impedances can be accomplished in various manners, includingproviding the necessary load impedance directly or the use of animpedance match circuit as described below.

When matching from a high impedance to a low impedance, a capacitor 7314and an inductor 7316 can be configured as shown in FIG. 73. Thecapacitor 7314 and the inductor 7316 constitute an L match, thecalculation of the component values being well known to those skilled inthe relevant arts.

The configuration of the input impedance match module 7006 and theoutput impedance match module 7008 are considered to be initial startingpoints for impedance matching, in accordance with the present invention.In some situations, the initial designs may be suitable without furtheroptimization. In other situations, the initial designs can be optimizedin accordance with other various design criteria and considerations.

As other optional optimizing structures and/or components are utilized,their affect on the characteristic impedance of the energy transfermodule should be taken into account in the match along with their ownoriginal criteria.

-   -   6.5 Tanks and Resonant Structures

Resonant tank and other resonant structures can be used to furtheroptimize the energy transfer characteristics of the invention. Forexample, resonant structures, resonant about the input frequency, can beused to store energy from the input signal when the switch is open, aperiod during which one may conclude that the architecture wouldotherwise be limited in its maximum possible efficiency. Resonant tankand other resonant structures can include, but are not limited to,surface acoustic wave (SAW) filters, dielectric resonators, diplexers,capacitors, inductors, etc.

An example embodiment is shown in FIG. 94A. Two additional embodimentsare shown in FIG. 88 and FIG. 97. Alternate implementations will beapparent to persons skilled in the relevant art(s) based on theteachings contained herein. Alternate implementations fall within thescope and spirit of the present invention. These implementations takeadvantage of properties of series and parallel (tank) resonant circuits.

FIG. 94A illustrates parallel tank circuits in a differentialimplementation. A first parallel resonant or tank circuit consists of acapacitor 9438 and an inductor 9420 (tank1). A second tank circuitconsists of a capacitor 9434 and an inductor 9436 (tank2).

As is apparent to one skilled in the relevant art(s), parallel tankcircuits provide:

-   -   low impedance to frequencies below resonance;    -   low impedance to frequencies above resonance; and    -   high impedance to frequencies at and near resonance.

In the illustrated example of FIG. 94A, the first and second tankcircuits resonate at approximately 920 Mhz. At and near resonance, theimpedance of these circuits is relatively high. Therefore, in thecircuit configuration shown in FIG. 94A, both tank circuits appear asrelatively high impedance to the input frequency of 950 Mhz, whilesimultaneously appearing as relatively low impedance to frequencies inthe desired output range of 50 Mhz.

An energy transfer signal 9442 controls a switch 9414. When the energytransfer signal 9442 controls the switch 9414 to open and close, highfrequency signal components are not allowed to pass through tank1 ortank2. However, the lower signal components (50 Mhz in this embodiment)generated by the system are allowed to pass through tank1 and tank2 withlittle attenuation. The effect of tank1 and tank2 is to further separatethe input and output signals from the same node thereby producing a morestable input and output impedance. Capacitors 9418 and 9440 act to storethe 50 Mhz output signal energy between energy transfer pulses.

Further energy transfer optimization is provided by placing an inductor9410 in series with a storage capacitor 9412 as shown. In theillustrated example, the series resonant frequency of this circuitarrangement is approximately 1 GHz. This circuit increases the energytransfer characteristic of the system. The ratio of the impedance ofinductor 9410 and the impedance of the storage capacitor 9412 ispreferably kept relatively small so that the majority of the energyavailable will be transferred to storage capacitor 9412 duringoperation. Exemplary output signals A and B are illustrated in FIGS. 94Band 94C, respectively.

In FIG. 94A, circuit components 9404 and 9406 form an input impedancematch. Circuit components 9432 and 9430 form an output impedance matchinto a 50 ohm resistor 9428. Circuit components 9422 and 9424 form asecond output impedance match into a 50 ohm resistor 9426. Capacitors9408 and 9412 act as storage capacitors for the embodiment. Voltagesource 9446 and resistor 9402 generate a 950 Mhz signal with a 50 ohmoutput impedance, which are used as the input to the circuit. Circuitelement 9416 includes a 150 Mhz oscillator and a pulse generator, whichare used to generate the energy transfer signal 9442.

FIG. 88 illustrates a shunt tank circuit 8810 in a single-endedto-single-ended system 8812. Similarly, FIG. 97 illustrates a shunt tankcircuit 9710 in a system 9712. The tank circuits 8810 and 9710 lowerdriving source impedance, which improves transient response. The tankcircuits 8810 and 9710 are able store the energy from the input signaland provide a low driving source impedance to transfer that energythroughout the aperture of the closed switch. The transient nature ofthe switch aperture can be viewed as having a response that, in additionto including the input frequency, has large component frequencies abovethe input frequency, (i.e. higher frequencies than the input frequencyare also able to effectively pass through the aperture). Resonantcircuits or structures, for example resonant tanks 8810 or 9710, cantake advantage of this by being able to transfer energy throughout theswitch's transient frequency response (i.e. the capacitor in theresonant tank appears as a low driving source impedance during thetransient period of the aperture).

The example tank and resonant structures described above are forillustrative purposes and are not limiting. Alternate configurations canbe utilized. The various resonant tanks and structures discussed can becombined or utilized independently as is now apparent.

-   -   6.6 Charge and Power Transfer Concepts

Concepts of charge transfer are now described with reference to FIGS.109A–F. FIG. 109A illustrates a circuit 10902, including a switch S anda capacitor 10906 having a capacitance C. The switch S is controlled bya control signal 10908, which includes pulses 19010 having apertures T.

In FIG. 109B, Equation 10 illustrates that the charge q on a capacitorhaving a capacitance C, such as the capacitor 10906, is proportional tothe voltage V across the capacitor, where:

-   -   q=Charge in Coulombs    -   C=Capacitance in Farads    -   V=Voltage in Volts    -   A=Input Signal Amplitude

Where the voltage V is represented by Equation 11, Equation 10 can berewritten as Equation 12. The change in charge Δq over time t isillustrated as in Equation 13 as Δq(t), which can be rewritten asEquation 14. Using the sum-to-product trigonometric identity of Equation15, Equation 14 can be rewritten as Equation 16, which can be rewrittenas equation 17.

Note that the sin term in Equation 11 is a function of the aperture Tonly. Thus, Δq(t) is at a maximum when T is equal to an odd multiple ofπ (i.e., π, 3π, 5π, . . . ). Therefore, the capacitor 10906 experiencesthe greatest change in charge when the aperture T has a value of π or atime interval representative of 180 degrees of the input sinusoid.Conversely, when T is equal to 2π, 4π, 6π, . . . , minimal charge istransferred.

Equations 18, 19, and 20 solve for q(t) by integrating Equation 10,allowing the charge on the capacitor 10906 with respect to time to begraphed on the same axis as the input sinusoid sin(t), as illustrated inthe graph of FIG. 109C. As the aperture T decreases in value or tendstoward an impulse, the phase between the charge on the capacitor C orq(t) and sin(t) tend toward zero. This is illustrated in the graph ofFIG. 109D, which indicates that the maximum impulse charge transferoccurs near the input voltage maxima. As this graph indicates,considerably less charge is transferred as the value of T decreases.

Power/charge relationships are illustrated in Equations 21–26 of FIG.109E, where it is shown that power is proportional to charge, andtransferred charge is inversely proportional to insertion loss.

Concepts of insertion loss are illustrated in FIG. 109F. Generally, thenoise figure of a lossy passive device is numerically equal to thedevice insertion loss. Alternatively, the noise figure for any devicecannot be less that its insertion loss. Insertion loss can be expressedby Equation 27 or 28.

From the above discussion, it is observed that as the aperture Tincreases, more charge is transferred from the input to the capacitor10906, which increases power transfer from the input to the output. Ithas been observed that it is not necessary to accurately reproduce theinput voltage at the output because relative modulated amplitude andphase information is retained in the transferred power.

-   -   6.7 Optimizing and Adjusting the Non-Negligible Aperture        Width/Duration        -   6.7.1 Varying Input and Output Impedances

In an embodiment of the invention, the energy transfer signal 6306 ofFIG. 63 is used to vary the input impedance seen by the EM Signal 1304and to vary the output impedance driving a load. An example of thisembodiment is described below using the gated transfer module 6404 shownin FIG. 68G, and in FIG. 82A. The method described below is not limitedto the gated transfer module 6404, as it can be applied to all of theembodiments of energy transfer module 6304.

In FIG. 82A, when switch 8206 is closed, the impedance looking intocircuit 8202 is substantially the impedance of storage moduleillustrated as the storage capacitance 8208, in parallel with theimpedance of the load 8212. When the switch 8206 is open, the impedanceat point 8214 approaches infinity. It follows that the average impedanceat point 8214 can be varied from the impedance of the storage moduleillustrated as the storage capacitance 8208, in parallel with the load8212, to the highest obtainable impedance when switch 8206 is open, byvarying the ratio of the time that switch 8206 is open to the timeswitch 8206 is closed. Since the switch 8206 is controlled by the energytransfer signal 8210, the impedance at point 8214 can be varied bycontrolling the aperture width of the energy transfer signal, inconjunction with the aliasing rate.

An example method of altering the energy transfer signal 6306 of FIG. 63is now described with reference to FIG. 71, where the circuit 7102receives the input oscillating signal 7106 and outputs a pulse trainshown as doubler output signal 7104. The circuit 7102 can be used togenerate the energy transfer signal 6306. Example waveforms of 7104 areshown on FIG. 72B.

It can be shown that by varying the delay of the signal propagated bythe inverter 7108, the width of the pulses in the doubler output signal7104 can be varied. Increasing the delay of the signal propagated byinverter 7108, increases the width of the pulses. The signal propagatedby inverter 7108 can be delayed by introducing a R/C low pass network inthe output of inverter 7108. Other means of altering the delay of thesignal propagated by inverter 7108 will be well known to those skilledin the art.

-   -   -   6.7.2 Real Time Aperture Control

In an embodiment, the aperture width/duration is adjusted in real time.For example, referring to the timing diagrams in FIGS. 98B–F, a clocksignal 9814 (FIG. 98B) is utilized to generate an energy transfer signal9816 (FIG. 98F), which includes energy transfer pluses 9818, havingvariable apertures 9820. In an embodiment, the clock signal 9814 isinverted as illustrated by inverted clock signal 9822 (FIG. 98D). Theclock signal 9814 is also delayed, as illustrated by delayed clocksignal 9824 (FIG. 98E). The inverted clock signal 9814 and the delayedclock signal 9824 are then ANDed together, generating an energy transfersignal 9816, which is active—energy transfer pulses 9818—when thedelayed clock signal 9824 and the inverted clock signal 9822 are bothactive. The amount of delay imparted to the delayed clock signal 9824substantially determines the width or duration of the apertures 9820. Byvarying the delay in real time, the apertures are adjusted in real time.

In an alternative implementation, the inverted clock signal 9822 isdelayed relative to the original clock signal 9814, and then ANDed withthe original clock signal 9814. Alternatively, the original clock signal9814 is delayed then inverted, and the result ANDed with the originalclock signal 9814.

FIG. 98A illustrates an exemplary real time aperture control system 9802that can be utilized to adjust apertures in real time. The example realtime aperture control system 9802 includes an RC circuit 9804, whichincludes a voltage variable capacitor 9812 and a resistor 9826. The realtime aperture control system 9802 also includes an inverter 9806 and anAND gate 9808. The AND gate 9808 optionally includes an enable input9810 for enabling/disabling the AND gate 9808. The RC circuit 9804. Thereal time aperture control system 9802 optionally includes an amplifier9828.

Operation of the real time aperture control circuit is described withreference to the timing diagrams of FIGS. 98B–F. The real time controlsystem 9802 receives the input clock signal 9814, which is provided toboth the inverter 9806 and to the RC circuit 9804. The inverter 9806outputs the inverted clock signal 9822 and presents it to the AND gate9808. The RC circuit 9804 delays the clock signal 9814 and outputs thedelayed clock signal 9824. The delay is determined primarily by thecapacitance of the voltage variable capacitor 9812. Generally, as thecapacitance decreases, the delay decreases.

The delayed clock signal 9824 is optionally amplified by the optionalamplifier 9828, before being presented to the AND gate 9808.Amplification is desired, for example, where the RC constant of the RCcircuit 9804 attenuates the signal below the threshold of the AND gate9808.

The AND gate 9808 ANDs the delayed clock signal 9824, the inverted clocksignal 9822, and the optional Enable signal 9810, to generate the energytransfer signal 9816. The apertures 9820 are adjusted in real time byvarying the voltage to the voltage variable capacitor 9812.

In an embodiment, the apertures 9820 are controlled to optimize powertransfer. For example, in an embodiment, the apertures 9820 arecontrolled to maximize power transfer. Alternatively, the apertures 9820are controlled for variable gain control (e.g. automatic gaincontrol—AGC). In this embodiment, power transfer is reduced by reducingthe apertures 9820.

As can now be readily seen from this disclosure, many of the aperturecircuits presented, and others, can be modified in the manner describedabove (e.g. circuits in FIGS. 68 H–K). Modification or selection of theaperture can be done at the design level to remain a fixed value in thecircuit, or in an alternative embodiment, may be dynamically adjusted tocompensate for, or address, various design goals such as receiving RFsignals with enhanced efficiency that are in distinctively differentbands of operation, e.g. RF signals at 900 MHz and 1.8 GHz.

-   -   6.8 Adding a Bypass Network

In an embodiment of the invention, a bypass network is added to improvethe efficiency of the energy transfer module. Such a bypass network canbe viewed as a means of synthetic aperture widening. Components for abypass network are selected so that the bypass network appearssubstantially lower impedance to transients of the switch module (i.e.,frequencies greater than the received EM signal) and appears as amoderate to high impedance to the input EM signal (e.g., greater that100 Ohms at the RF frequency).

The time that the input signal is now connected to the opposite side ofthe switch module is lengthened due to the shaping caused by thisnetwork, which in simple realizations may be a capacitor or seriesresonant inductor-capacitor. A network that is series resonant above theinput frequency would be a typical implementation. This shaping improvesthe conversion efficiency of an input signal that would otherwise, ifone considered the aperture of the energy transfer signal only, berelatively low in frequency to be optimal.

For example, referring to FIG. 95 a bypass network 9502 (shown in thisinstance as capacitor 9512), is shown bypassing switch module 9504. Inthis embodiment the bypass network increases the efficiency of theenergy transfer module when, for example, less than optimal aperturewidths were chosen for a given input frequency on the energy transfersignal 9506. The bypass network 9502 could be of differentconfigurations than shown in FIG. 95. Such an alternate is illustratedin FIG. 90. Similarly, FIG. 96 illustrates another example bypassnetwork 9602, including a capacitor 9604.

The following discussion will demonstrate the effects of a minimizedaperture and the benefit provided by a bypassing network. Beginning withan initial circuit having a 550 ps aperture in FIG. 103, its output isseen to be 2.8 mVpp applied to a 50 ohm load in FIG. 107A. Changing theaperture to 270 ps as shown in FIG. 104 results in a diminished outputof 2.5 Vpp applied to a 50 ohm load as shown in FIG. 107B. To compensatefor this loss, a bypass network may be added, a specific implementationis provided in FIG. 105. The result of this addition is that 3.2 Vpp cannow be applied to the 50 ohm load as shown in FIG. 108A. The circuitwith the bypass network in FIG. 105 also had three values adjusted inthe surrounding circuit to compensate for the impedance changesintroduced by the bypass network and narrowed aperture. FIG. 106verifies that those changes added to the circuit, but without the bypassnetwork, did not themselves bring about the increased efficiencydemonstrated by the embodiment in FIG. 105 with the bypass network. FIG.108B shows the result of using the circuit in FIG. 106 in which only1.88 Vpp was able to be applied to a 50 ohm load.

-   -   6.9 Modifying the Energy Transfer Signal Utilizing-Feedback

FIG. 69 shows an embodiment of a system 6901 which uses down-convertedSignal 1308B as feedback 6906 to control various characteristics of theenergy transfer module 6304 to modify the down-converted signal 1308B.

Generally, the amplitude of the down-converted signal 1308B varies as afunction of the frequency and phase differences between the EM signal1304 and the energy transfer signal 6306. In an embodiment, thedown-converted signal 1308B is used as the feedback 6906 to control thefrequency and phase relationship between the EM signal 1304 and theenergy transfer signal 6306. This can be accomplished using the examplelogic in FIG. 85A. The example circuit in FIG. 85A can be included inthe energy transfer signal module 6902. Alternate implementations willbe apparent to persons skilled in the relevant art(s) based on theteachings contained herein. Alternate implementations fall within thescope and spirit of the present invention. In this embodiment astate-machine is used as an example.

In the example of FIG. 85A, a state machine 8504 reads an analog todigital converter, A/D 8502, and controls a digital to analog converter,DAC 8506. In an embodiment, the state machine 8504 includes 2 memorylocations, Previous and Current, to store and recall the results ofreading A/D 8502. In an embodiment, the state machine 8504 utilizes atleast one memory flag.

The DAC 8506 controls an input to a voltage controlled oscillator, VCO8508. VCO 8508 controls a frequency input of a pulse generator 8510,which, in an embodiment, is substantially similar to the pulse generatorshown in FIG. 68J. The pulse generator 8510 generates energy transfersignal 6306.

In an embodiment, the state machine 8504 operates in accordance with astate machine flowchart 8519 in FIG. 85B. The result of this operationis to modify the frequency and phase relationship between the energytransfer signal 6306 and the EM signal 1304, to substantially maintainthe amplitude of the down-converted signal 1308B at an optimum level.

The amplitude of the down-converted signal 1308B can be made to varywith the amplitude of the energy transfer signal 6306. In an embodimentwhere the switch module 6502 is a FET as shown in FIG. 66A, wherein thegate 6604 receives the energy transfer signal 6306, the amplitude of theenergy transfer signal 6306 can determine the “on” resistance of theFET, which affects the amplitude of the down-converted signal 1308B. Theenergy transfer signal module 6902, as shown in FIG. 85C, can be ananalog circuit that enables an automatic gain control function.Alternate implementations will be apparent to persons skilled in therelevant art(s) based on the teachings contained herein. Alternateimplementations fall within the scope and spirit of the presentinvention.

-   -   6.10 Other Implementations

The implementations described above are provided for purposes ofillustration. These implementations are not intended to limit theinvention. Alternate implementations, differing slightly orsubstantially from those described herein, will be apparent to personsskilled in the relevant art(s) based on the teachings contained herein.Such alternate implementations fall within the scope and spirit of thepresent invention.

7. Example Energy Transfer Downconverters

Example implementations are described below for illustrative purposes.The invention is not limited to these examples.

FIG. 86 is a schematic diagram of an exemplary circuit to down convert a915 MHz signal to a 5 MHz signal using a 101.1 MHz clock.

FIG. 87 shows example simulation waveforms for the circuit of FIG. 86.Waveform 8602 is the input to the circuit showing the distortions causedby the switch closure. Waveform 8604 is the unfiltered output at thestorage unit. Waveform 8606 is the impedance matched output of thedownconverter on a different time scale.

FIG. 88 is a schematic diagram of an exemplary circuit to downconvert a915 MHz signal to a 5 MHz signal using a 101.1 MHz clock. The circuithas additional tank circuitry to improve conversion efficiency.

FIG. 89 shows example simulation waveforms for the circuit of FIG. 88.Waveform 8802 is the input to the circuit showing the distortions causedby the switch closure. Waveform 8804 is the unfiltered output at thestorage unit. Waveform 8806 is the output of the downconverter after theimpedance match circuit.

FIG. 90 is a schematic diagram of an exemplary circuit to downconvert a915 MHz signal to a 5 MHz signal using a 101.1 MHz clock. The circuithas switch bypass circuitry to improve conversion efficiency.

FIG. 91 shows example simulation waveforms for the circuit of FIG. 90.Waveform 9002 is the input to the circuit showing the distortions causedby the switch closure. Waveform 9004 is the unfiltered output at thestorage unit. Waveform 9006 is the output of the downconverter after theimpedance match circuit.

FIG. 92 shows a schematic of the example circuit in FIG. 86 connected toan FSK source that alternates between 913 and 917 MHz, at a baud rate of500 Kbaud. FIG. 93 shows the original FSK waveform 9202 and thedownconverted waveform 9204 at the output of the load impedance matchcircuit.

IV. Additional Embodiments

Additional aspects/embodiments of the invention are considered in thissection.

In one embodiment of the present invention there is provided a method oftransmitting information between a transmitter and a receiver comprisingthe steps of transmitting a first series of signals each having a knownperiod from the transmitter at a known first repetition rate; samplingby the receiver each signal in the first series of signals a single timeand for a known time interval the sampling of the first series ofsignals being at a second repetition rate that is a rate different fromthe first repetition rate by a known amount; and generating by thereceiver an output signal indicative of the signal levels sampled instep B and having a period longer than the known period of a transmittedsignal.

In another embodiment of the invention there is provided a communicationsystem comprising a transmitter means for transmitting a first series ofsignals of known period at a known first repetition rate, a receivermeans for receiving the first series of signals, the receiver meansincluding sampling means for sampling the signal level of each signalfirst series of signals for a known time interval at a known secondrepetition rate, the second repetition rate being different from thefirst repetition rate by a known amount as established by the receivermeans. The receiver means includes first circuit means for generating afirst receiver output signal indicative of the signal levels sampled andhaving a period longer than one signal of the first series of signals.The transmitter means includes an oscillator for generating anoscillator output signal at the first repetition rate, switch means forreceiving the oscillator output signal and for selectively passing theoscillator output signal, waveform generating means for receiving theoscillator output signal for generating a waveform generator outputsignal having a time domain and frequency domain established by thewaveform generating means.

The embodiment of the invention described herein involves a single ormulti-user communications system that utilizes coherent signals toenhance the system performance over conventional radio frequency schemeswhile reducing cost and complexity. The design allows direct conversionof radio frequencies into baseband components for processing andprovides a high level of rejection for signals that are not related to aknown or controlled slew rate between the transmitter and receivertiming oscillators. The system can be designed to take advantage ofbroadband techniques that further increase its reliability and permit ahigh user density within a given area. The technique employed allows thesystem to be configured as a separate transmitter-receiver pair or atransceiver.

The basic objectives of the present system is to provide a newcommunication technique that can be applied to both narrow and wide bandsystems. In its most robust form, all of the advantages of wide bandcommunications are an inherent part of the system and the invention doesnot require complicated and costly circuitry as found in conventionalwide band designs. The communications system utilizes coherent signalsto send and receive information and consists of a transmitter and areceiver in its simplest form. The receiver contains circuitry to turnits radio frequency input on and off in a known relationship in time tothe transmitted signal. This is accomplished by allowing the transmittertiming oscillator and the receiver timing oscillator to operate atdifferent but known frequencies to create a known slew rate between theoscillators. If the slew rate is small compared to the timing oscillatorfrequencies, the transmitted waveform will appear stable in time, i.e.,coherent (moving at the known slew rate) to the receiver's switchedinput. The transmitted waveform is the only waveform that will appearstable in time to the receiver and thus the receiver's input can beaveraged to achieve the desired level filtering of unwanted signals.This methodology makes the system extremely selective withoutcomplicated filters and complex encoding and decoding schemes and allowsthe direct conversion of radio frequency energy from an antenna or cableto baseband frequencies with a minimum number of standard componentsfurther reducing cost and complexity. The transmitted waveform can be aconstant carrier (narrowband), a controlled pulse (wideband andultra-wideband) or a combination of both such as a dampened sinusoidalwave and or any arbitrary periodic waveform thus the system can bedesigned to meet virtually any bandwidth requirement. Simple standardmodulation and demodulation techniques such as AM and Pulse WidthModulation can be easily applied to the system.

Depending on the system requirements such as the rate of informationtransfer, the process gain, and the intended use, there are multiplepreferred embodiments of the invention. The embodiment discussed hereinwill be the amplitude and pulse width modulated system. It is one of thesimplest implementations of the technology and has many commoncomponents with the subsequent systems. A amplitude modulatedtransmitter consists of a Transmitter Timing Oscillator, a Multiplier, aWaveform Generator, and an Optional Amplifier. The Transmitter TimingOscillator frequency can be determined by a number of resonate circuitsincluding an inductor and capacitor, a ceramic resonator, a SAWresonator, or a crystal. The output waveform is sinusoidal, although asquarewave oscillator would produce identical system performance.

The Multiplier component multiplies the Transmitter Timing Oscillatoroutput signal by 0 or 1 or other constants, K1 and K2, to switch theoscillator output on and off to the Waveform Generator. In thisembodiment, the information input can be digital data or analog data inthe form of pulse width modulation. The Multiplier allows theTransmitter Timing Oscillator output to be present at the WaveformGenerator input when the information input is above a predeterminedvalue. In this state the transmitter will produce an output waveform.When the information input is below a predetermined value, there is noinput to the Waveform Generator and thus there will be no transmitteroutput waveform. The output of the Waveform Generator determines thesystem's bandwidth in the frequency domain and consequently the numberof users, process gain immunity to interference and overallreliability), the level of emissions on any given frequency, and theantenna or cable requirements. The Waveform Generator in this examplecreates a one cycle pulse output which produces an ultra-wideband signalin the frequency domain. An optional power Amplifier stage boosts theoutput of the Waveform Generator to a desired power level.

With reference now to the drawings, the amplitude and pulse widthmodulated transmitter in accord with the present invention is depictedat numeral 13000 in FIGS. 130 and 131. The Transmitter Timing Oscillator13002 is a crystal-controlled oscillator operating at a frequency of 25MHZ. Multiplier 13004 includes a two-input NAND gate 13102 controllingthe gating of oscillator 13002 output to Waveform Generator 13006.Waveform Generator 13006 produces a pulse output as depicted at 13208 inFIGS. 132A–132D and 133, which produces a frequency spectrum 13402 inFIG. 134. Amplifier 13008 is optional. The transmitter 13000 output isapplied to antenna or cable 13010, which as understood in the art, maybe of various designs as appropriate in the circumstances.

FIGS. 132A–132D, 133 and 134 illustrate the various signals present intransmitter 13000. The output of transmitter 13000 in FIG. 132A may beeither a sinusoidal or squarewave signal 13202 that is provided as oneinput into NAND gate 13102. Gate 13102 also receives an informationsignal 13204 in FIG. 132B which, in the embodiment shown, is digital inform. The output 13206 of Multiplier 13004 can be either sinusoidal orsquarewave depending upon the original signal 13202. Waveform Generator13006 provides an output of a single cycle impulse signal 13208. Thesingle cycle impulse 13210 varies in voltage around a static level 13212and is created at 40 nanoseconds intervals. In the illustratedembodiment, the frequency of transmitter 13002 is 25 MHZ andaccordingly, one cycle pulses of 1.0 GHZ are transmitted every 40nanoseconds during the total time interval that gate 13102 is “on” andpasses the output of transmitter oscillator 13002.

FIG. 135 shows the preferred embodiment receiver block diagram torecover the amplitude or pulse width modulated information and consistsof a Receiver Timing Oscillator 13510, Waveform Generator 13508, RFSwitch Fixed or Variable Integrator 13506, Decode Circuit 13514, twooptional Amplifier/Filter stages 13504 and 13512, antenna or cable input13502, and Information Output 13516. The Receiver Timing Oscillator13510 frequency can be determined by a number of resonate circuitsincluding an inductor and capacitor, a ceramic resonator, a SAWresonator, or a crystal. As in the case of the transmitter, theoscillator 13510 shown here is a crystal oscillator. The output waveformis a squarewave, although a sinewave oscillator would produce identicalsystem performance. The squarewave timing oscillator output 13602 isshown in FIG. 136A. The Receiver Timing Oscillator 13510 is designed tooperate within a range of frequencies that creates a known range of slewrates relative to the Transmitter Timing Oscillator 13002. In thisembodiment, the Transmitter Timing Oscillator 13002 frequency is 25 MHZand the Receiver Timing Oscillator 13510 outputs between 25.0003 MHZ and25.0012 MHZ which creates a +300 to +1200 Hz slew rate.

The Receiver Timing Oscillator 13510 is connected to the WaveformGenerator 13508 which shapes the oscillator signal into the appropriateoutput to control the amount of the time that the RF switch 13506 is onand off. The on-time of the RF switch 13506 should be less than ½ of acycle ( 1/10 of a cycle is preferred) or in the case of a single pulse,no wider than the pulse width of the transmitted waveform or the signalgain of the system will be reduced. Examples are illustrated in TableA1. Therefore the output of the Waveform Generator 13508 is a pulse ofthe appropriate width that occurs once per cycle of the receiver timingoscillator 13510. The output 13604 of the Waveform Generator is shown inFIG. 136B.

TABLE A1 Transmitted Waveform Gain Limit on-time Preferred on-timeSingle 1 nanosecond pulse 1 nanosecond 100 picoseconds 1 Gigahertz 1, 2,3 . . . etc. 500 picoseconds 50 picoseconds cycle output 10 Gigahertz 1,2, 3 . . . etc. 50 picoseconds 5 picoseconds cycle output

The RF Switch/Integrator 13506 samples the RF signal 13606 shown in FIG.136C when the Waveform Generator output 13604 is below a predeterminedvalue. When the Waveform Generator output 13604 is above a predeterminedvalue, the RF Switch 13506 becomes a high impedance node and allows theIntegrator to hold the last RF signal sample 13606 until the next cycleof the Waveform Generator 13508 output. The Integrator section of 13506is designed to charge the Integrator quickly (fast attack) and dischargethe Integrator at a controlled rate (slow decay). This embodimentprovides unwanted signal rejection and is a factor in determining thebaseband frequency response of the system. The sense of the switchcontrol is arbitrary depending on the actual hardware implementation.

In an embodiment of the present invention, the gating or sampling rateof the receiver 13500 is 300 Hz higher than the 25 MHZ transmission ratefrom the transmitter 13000. Alternatively, the sampling rate could beless than the transmission rate. The difference in repetition ratesbetween the transmitter 13000 and receiver 13500, the “slew rate,” is300 Hz and results in a controlled drift of the sampling pulses over thetransmitted pulse which thus appears “stable” in time to the receiver13500. With reference now to FIGS. 132A–132D and 136A–136G, an exampleis illustrated for a simple case of an output signal 13608 (FIG. 136D)that is constructed of four samples from four RF input pulses 13606 forease of explanation. As can be clearly seen, by sampling the RF pulses13606 passed when the transmitter information signal 13204 (FIG. 132B)is above a predetermine threshold the signal 13608 is a replica of asignal 13606 but mapped into a different time base. In the case of thisexample, the new time base has a period four times longer than real timesignal. The use of an optional amplifier/filter 13512 results in afurther refinement of the signal 13608 which is present in FIG. 136E assignal 13610.

Decode Circuitry 13514 extracts the information contained in thetransmitted signal and includes a Rectifier that rectifies signal 13608or 13610 to provide signal 13612 in FIG. 136G. The Variable ThresholdGenerator circuitry in circuit 13514 provides a DC threshold signallevel 13614 for signal 13610 that is used to determine a high(transmitter output on) or low (transmitter output off) and is shown inFIG. 136G. The final output signal 13616 in FIG. 136F is created by anoutput voltage comparator in circuit 13514 that combines signals 13612and 13614 such that when the signal 13612 is a higher voltage thansignal 13614, the information output signal goes high. Accordingly,signal 13616 represents, for example, a digital “1” that is nowtime-based to a 1:4 expansion of the period of an original signal 13606.While this illustration provides a 4:1 reduction in frequency, it issometimes desired to provide a reduction of more than 50,000:1; in thepreferred embodiment, 100,000:1 or greater is achieved. This results ina shift directly from RF input frequency to low frequency basebandwithout the requirement of expensive intermediate circuitry that wouldhave to be used if only a 4:1 conversion was used as a first stage.Table A2 provides information as to the time base conversion andincludes examples.

TABLE A2 Units s = 1 ps = 1 · 10¹² ns = 1 · 10⁻⁹ us = 1 · 10⁻⁶ MHz = 1 ·10⁶ KHz = 1 · 10³ Receiver Timing Oscillator Frequency = 25.0003 MHzTransmitter Timing Oscillator Frequency = 25 MHz${period} = \frac{1}{{Transmitter}\mspace{14mu}{Timing}\mspace{14mu}{Oscillator}\mspace{14mu}{Frequency}}$period = 40 ns ${{slew}\mspace{14mu}{rate}} = \frac{1}{\begin{matrix}{{{Receiver}\mspace{14mu}{Timing}\mspace{14mu}{Oscillator}\mspace{14mu}{Frequency}} -} \\{{Transmitter}\mspace{14mu}{Timing}\mspace{14mu}{Oscillator}\mspace{14mu}{Frequency}}\end{matrix}}$ slew rate = 0.003 s${{time}\mspace{14mu}{base}\mspace{14mu}{multiplier}} = {\frac{{slew}\mspace{14mu}{rate}}{period}{seconds}\mspace{14mu}{per}\mspace{14mu}{nanosecond}}$time base multiplier = 8.333 · 10⁴ Example 1: 1 nanosecond translatesinto 83.33 microseconds time base = (1 ns) · time base multiplier timebase = 83.333 us Example 2: 2 Gigahertz translates into 24 Kilohertz 2Gigahertz = 500 picosecond period time base = (500 ps) · time basemultiplier time base = 41.667 us${frequency} = \frac{1}{{time}\mspace{14mu}{base}}$ frequency = 24 KHz

In the illustrated preferred embodiment, the signal 13616 in FIG. 136Fhas a period of 83.33 usec, a frequency of 12 KHz and it is producedonce every 3.3 msec for a 300 Hz slew rate. Stated another way, thesystem is converting a 1 gigahertz transmitted signal into an 83.33microsecond signal.

Accordingly, the series of RF pulses 13210 that are transmitted duringthe presence of an “on” signal at the information input gate 13102 areused to reconstruct the information input signal 13204 by sampling theseries of pulses at the receiver 13500. The system is designed toprovide an adequate number of RF inputs 13606 to allow for signalreconstruction.

An optional Amplifier/Filter stage or stages 13504 and 13512 may beincluded to provide additional receiver sensitivity, bandwidth controlor signal conditioning for the Decode Circuitry 13514. Choosing anappropriate time base multiplier will result in a signal at the outputof the Integrator 13506 that can be amplified and filtered withoperational amplifiers rather than RF amplifiers with a resultantsimplification of the design process. The signal 13610 in FIG. 136Eillustrates the use of Amplifier/Filter 13512 (FIG. 137). The optionalRF amplifier 13504 shown as the first stage of the receiver should beincluded in the design when increased sensitivity and/or additionalfiltering is required. Example receiver schematics are shown in FIGS.137–139.

FIGS. 140–143 illustrate different pulse output signals 14002 and 14202and their respective frequency domain at 14102 and 14302. As can be seenfrom FIGS. 140 and 141, the half-cycle signal 14002 generates a spectrumless subject to interference than the single cycle of FIG. 133 and the10-cycle pulse of FIG. 142. The various outputs determine the system'simmunity to interference, the number of users in a given area, and thecable and antenna requirements. FIGS. 133 and 134 illustrate examplepulse outputs.

FIGS. 144 and 145 show example differential receiver designs. The theoryof operation is similar to the non-differential receiver of FIG. 135except that the differential technique provides an increased signal tonoise ratio by means of common mode rejection. Any signal impressed inphase at both inputs on the differential receiver will attenuated by thedifferential amplifier shown in FIGS. 144 and 145 and conversely anysignal that produces a phase difference between the receiver inputs willbe amplified.

FIGS. 146 and 147 illustrate the time and frequency domains of a narrowband/constant carrier signal in contrast to the ultra-wide band signalsused in the illustrated embodiment.

V. Conclusions

Example embodiments of the methods, systems, and components of thepresent invention have been described herein. As noted elsewhere, theseexample embodiments have been described for illustrative purposes only,and are not limiting. Other embodiments are possible and are covered bythe invention. Such other embodiments include but are not limited tohardware, software, and software/hardware implementations of themethods, systems, and components of the invention. Such otherembodiments will be apparent to persons skilled in the relevant art(s)based on the teachings contained herein. Thus, the breadth and scope ofthe present invention should not be limited by any of theabove-described exemplary embodiments, but should be defined only inaccordance with the following claims and their equivalents.

1. A method for down-converting an electromagnetic signal, comprising:periodically coupling an electromagnetic signal that includes a carriersignal to an energy storage device and a load, wherein the periodiccouplings occur at a rate less than twice the frequency of the carriersignal; providing, during the periodic couplings, energy from theelectromagnetic signal to the energy storage device, thereby changing anamount of energy stored by the energy storage device; providing, duringthe periodic couplings, energy from the electromagnetic signal to theload; and providing, between the periodic couplings, energy from theenergy storage device to the load, thereby changing the amount of energystored by the energy storage device; whereby the energy provided to theload forms a down-converted signal.
 2. The method of claim 1, whereinthe periodic couplings have a duration greater than a quarter cycle ofthe carrier signal.
 3. The method of claim 1, wherein the periodiccouplings have a duration equal to a half cycle of the carrier signal.4. The method of claim 1, wherein the periodic couplings have a durationsubstantially equal to a half cycle of the carrier signal.
 5. The methodof claim 1, wherein the periodic couplings have a duration just equal toa half cycle of the carrier signal.
 6. The method of claim 1, whereinthe electromagnetic signal comprises an amplitude modulated signal. 7.The method of claim 1, wherein the electromagnetic signal comprises afrequency modulated signal.
 8. The method of claim 1, wherein theelectromagnetic signal comprises a phase modulated signal.
 9. The methodof claim 1, wherein the energy provided to the load forms anintermediate frequency signal.
 10. The method of claim 1, wherein theenergy provided to the load forms a baseband signal.
 11. The method ofclaim 1, wherein the energy storage device comprises a capacitor. 12.The method of claim 1, wherein the periodic couplings are achieved usinga switching device.
 13. A method for down-converting an electromagneticsignal that includes a carrier signal using a circuit that includes anenergy storage device, a switch, and a load, wherein the switch and theload are coupled in parallel between a port of the energy storage deviceand a circuit node, the method comprising: alternately closing andopening the switch at a frequency less than twice the frequency of thecarrier signal; providing, during each of the closings of the switch,energy from the electromagnetic signal to the energy storage device,thereby changing an amount of energy stored by the energy storagedevice; and providing, during each of the openings of the switch, energyfrom the energy storage device to the load, thereby changing the amountof energy stored by the energy storage device; whereby the energyprovided to the load forms a down-converted signal.
 14. The method ofclaim 13, further comprising: providing, during each of the openings ofthe switch, energy from the electromagnetic signal to the load.
 15. Themethod of claim 13, wherein each of the closings of the switch has aduration greater than a quarter cycle of the carrier signal.
 16. Themethod of claim 13, wherein each of the closings of the switch has aduration equal to a half cycle of the carrier signal.
 17. The method ofclaim 13, wherein each of the closings of the switch has a durationsubstantially equal to a half cycle of the carrier signal.
 18. Themethod of claim 13, wherein each of the closings of the switch has aduration just equal to a half cycle of the carrier signal.
 19. Themethod of claim 13, wherein the electromagnetic signal comprises anamplitude modulated signal.
 20. The method of claim 13, wherein theelectromagnetic signal comprises a frequency modulated signal.
 21. Themethod of claim 13, wherein the electromagnetic signal comprise a phasemodulated signal.
 22. The method of claim 13, wherein the energyprovided to the load forms an intermediate frequency signal.
 23. Themethod of claim 13, wherein the energy provided to the load forms abaseband signal.
 24. The method of claim 13, wherein the energy storagedevice comprises a capacitor.